Fracturing drilling drainage coal mine roof aquifer drainage method based on microseism

Abstract

The invention discloses a micro-seismic-based fracturing drilling drainage coal mine roof aquifer drainage method, which has the advantages that a continuous drainage network formed by deep and shallow hole collaborative design relieves the displacement limitation of single deep hole drainage; and water in the aquifer can flow into the goaf more smoothly. Through combination of retreat staged fracturing and a static fracturing agent, the fracture range is effectively expanded, branch fractures are increased, and the permeability coefficient of the aquifer is remarkably improved. The micro-seismic monitoring system monitors crack extension in real time and dynamically adjusts fracturing parameters, and construction accuracy and safety are improved. And through real-time monitoring and parameter adjustment, crack extension is effectively controlled, the instability risk of the top plate is reduced, and the construction safety is improved. The method can adapt to roof aquifer conditions with different lithology and different burial depths, has high universality, and provides effective technical support for coal mine roof water disaster prevention and control.

Description

Technical Field

[0001] This invention relates to the field of coal mine roof drainage technology, specifically to a method for draining aquifers from coal mine roofs using micro-vibration fracturing boreholes. Background Technology

[0002] Aquifers in the roof of coal mines are one of the main sources of water hazards underground. They are characterized by high water content, great depth, and low permeability. If drainage is not timely, they can easily lead to roof water inrush accidents, causing serious consequences. According to statistics, roof aquifer water hazards account for more than 30% of coal mine water hazard accidents in my country, making them a key factor restricting safe coal mine production.

[0003] Among related technologies, prevention and control methods mainly include deep-hole drainage and hydraulic fracturing for permeability enhancement and drainage. Deep-hole drainage involves drilling deep holes above the goaf to directly drain water into the aquifer. However, due to limitations in single-point layout, the drainage capacity of a single borehole is insufficient, the range and direction of fracture propagation are difficult to control, and the improvement in permeability coefficient is limited. It is difficult to effectively cover the water-rich area of ​​the aquifer and cannot meet the demand for rapid drainage of the roof aquifer for efficient production. Hydraulic fracturing, on the other hand, increases the permeability coefficient by pumping in high-pressure fluid to form fractures. However, it suffers from problems such as limited fracture range, difficulty in controlling the propagation direction, potential roof instability, and insignificant improvement in permeability coefficient. In addition, existing methods lack real-time monitoring of the fracturing process, making it difficult to dynamically adjust fracturing parameters, further exacerbating the uncertainty of fracture propagation and the risk of roof instability. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention propose a method for draining aquifers from the roof of coal mines using micro-vibration fracturing boreholes.

[0006] The present invention provides a method for draining aquifers from the roof of coal mines using microseismic fracturing boreholes, comprising the following steps:

[0007] S1. In the roof above the goaf of a coal mine, at least one deep hole and at least one shallow hole are constructed to form a drainage channel network covering the aquifer and transition layer; the end point of the deep hole penetrates the roof of the coal seam and enters the interior of the aquifer, and the end point of the shallow hole is located in the transition layer below the aquifer. S2. The deep hole is subjected to a backward segmented hydraulic fracturing process to form multiple hydraulic fracturing fractures inside the aquifer. S3. Perform a single hydraulic fracturing operation on the bottom of the shallow hole to form radial fractures within the transition layer; S4. Inject a static fracturing agent into the deep and shallow holes where hydraulic fracturing has been completed to expand the hydraulic fracturing fractures and form static fracturing fractures. S5. During the hydraulic fracturing process in steps S2 and S3, a microseismic monitoring system arranged around the borehole is used to monitor the fracture propagation range in real time, and the fracturing construction parameters are dynamically adjusted according to the monitoring results.

[0008] In some embodiments, in step S1, the distance between the deep hole and the shallow hole is controlled to be 15m-30m; the depth of the shallow hole is 10m-15m below the bottom plate of the aquifer.

[0009] In some embodiments, in step S1, during drilling, the verticality of the borehole is ensured by using drilling-while-drilling inclination measurement technology; after drilling is completed, the sediment at the bottom of the borehole is flushed with high-pressure water with a pressure of ≥5MPa for a duration of ≥10min.

[0010] In some embodiments, step S2 specifically includes: Based on the depth of the deep hole, it is divided into 3-5 fracturing sections, each with a length of 6m-15m; A double-sealing perforator is used to seal the upper and lower ends of the target fracturing section, forming a closed fracturing space; Fracturing is performed by pumping clean water into the fracturing space using a high-pressure pump, with the fracturing pressure controlled at 25MPa-35MPa and maintained for 25min-35min. Following the sequence from the bottom of the borehole to the top, the sealing and fracturing operations were repeated for each fracturing section.

[0011] In some embodiments, when dividing the fracturing sections, the section length is adjusted according to the aquifer lithology: the section length of sandstone aquifers is increased, and the section length of mudstone aquifers is shortened.

[0012] In some embodiments, step S3 specifically includes: The sealing device is inserted 20cm-35cm from the bottom of the shallow hole and expanded and fixed to form a closed fracturing space. Water is pumped into the fracturing space for fracturing at a pressure of 15MPa-25MPa for 15-25 minutes.

[0013] In some embodiments, in step S4, the method of injecting the static cracking agent is as follows: the static cracking agent and water are stirred into a paste at a ratio of 1:0.3, and injected using a grouting pump at a pressure of 1MPa-2MPa, with an injection volume of 1.2-1.5 times the pore volume; after injection, wait 24h-48h for the cracking agent to fully react.

[0014] In some embodiments, in step S5, the microseismic monitoring system includes a three-component microseismic sensor, a data acquisition instrument, and analysis software arranged in boreholes in the roof of the roadway within 20m around the borehole; the sensor is coupled to the surrounding rock with cement mortar, and the analysis software is used to calculate the location of microseismic events in real time to invert the fracture propagation range.

[0015] In some embodiments, step S5, dynamically adjusting the fracturing construction parameters based on the microseismic monitoring results, includes: stopping fracturing when the fracture propagation range reaches the design requirements; increasing the fracturing pressure or displacement when the fracture propagation rate is slow; and reducing the fracturing pressure when the fracture propagation exceeds the design range.

[0016] In some embodiments, the deep holes and shallow holes work together to form a continuous drainage network for diverting aquifer water along the expanded fracture network to the goaf.

[0017] This invention presents a microseismic-based fracturing borehole drainage method for aquifers in coal mine roofs. The continuous drainage network formed by the coordinated design of deep and shallow boreholes alleviates the discharge limitations of single deep boreholes, allowing aquifer water to flow more smoothly into the goaf. The combination of retreating segmented fracturing and static fracturing agents effectively expands the fracture range, increases branch fractures, and significantly improves the aquifer's permeability coefficient. A microseismic monitoring system monitors fracture propagation in real time and dynamically adjusts fracturing parameters, improving the accuracy and safety of the operation. Through real-time monitoring and parameter adjustment, fracture propagation is effectively controlled, reducing the risk of roof instability and enhancing construction safety. This method is adaptable to roof aquifer conditions of different lithologies and burial depths, possessing strong universality and providing effective technical support for the prevention and control of water hazards in coal mine roofs. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for draining aquifers from the roof of a coal mine based on micro-vibration fracturing boreholes, according to an embodiment of the present invention.

[0019] Figure 2 Schematic diagram of drilling for drainage of water-bearing aquifers at varying depths in the roof of a coal mine; Figure 3 This is a schematic diagram of the initial permeability enhancement of an aquifer through hydraulic fracturing. Figure 4 This is a schematic diagram of static fracturing and secondary permeability enhancement in an aquifer. 1. Goaf; 2. Deep borehole; 3. Shallow borehole; 4. Aquifer; 5. Coal seam; 6. Hydraulic fracturing fracture; 7. Static fracturing agent; 8. Static fracturing fracture; 9. Sealing device. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] like Figures 1 to 4 As shown in the figure, the method for draining aquifers from the roof of a coal mine based on micro-vibration fracturing boreholes according to an embodiment of the present invention includes the following steps: S1. In the roof above the goaf 1 of the coal mine, at least one deep hole 2 and at least one shallow hole 3 are constructed to form a drainage channel network covering the aquifer 4 and the transition layer; the final hole of the deep hole 2 penetrates the roof of the coal seam 5 and enters the interior of the aquifer 4, and the final hole of the shallow hole 3 is located in the transition layer below the aquifer 4. S2. A retreating segmented hydraulic fracturing process is used for deep hole 2 to form multiple hydraulic fracturing fractures 6 inside aquifer 4. S3. Perform a single hydraulic fracturing operation on the bottom of shallow hole 3 to form radial fractures within the transition layer; S4. Inject static fracturing agent 7 into the deep hole 2 and shallow hole 3 that have completed hydraulic fracturing to expand the hydraulic fracturing fracture 6 and form static fracturing fracture 8. S5. During the hydraulic fracturing process in steps S2 and S3, a microseismic monitoring system arranged around the borehole is used to monitor the fracture propagation range in real time, and the fracturing construction parameters are dynamically adjusted according to the monitoring results.

[0022] In the implementation of the microseismic fracturing borehole drainage method for aquifers in coal mines, as described in this invention, firstly, deep holes 2 and shallow holes 3 are drilled in the roof above the goaf 1 of the coal mine. Deep holes 2 penetrate the roof and enter the aquifer 4, while shallow holes 3 are located in the transition layer below the aquifer 4. The deep and shallow holes 3 form a drainage channel network, covering the aquifer 4 and the transition layer. Retreating segmented hydraulic fracturing is performed on the deep holes 2 to create multiple fracture segments; a single hydraulic fracturing is performed on the bottom of the shallow holes 3 to create radial fractures. A static fracturing agent 7 is injected into the hydraulically fractured deep holes 2 and shallow holes 3 to expand the fractures. During the fracturing process, a microseismic monitoring system is used to monitor the fracture expansion in real time, and the fracturing parameters are dynamically adjusted based on the monitoring results.

[0023] This invention presents a microseismic-based fracturing borehole drainage method for aquifers in coal mine roofs. The continuous drainage network formed by the coordinated design of deep and shallow boreholes (3) alleviates the discharge limitations of a single deep borehole (2), allowing water from the aquifer (4) to flow more smoothly into the goaf (1). The combination of retreating segmented fracturing and static fracturing agent (7) effectively expands the fracture range, increases branch fractures, and significantly improves the permeability coefficient of the aquifer (4). The microseismic monitoring system monitors fracture propagation in real time and dynamically adjusts fracturing parameters, improving the accuracy and safety of the operation. Through real-time monitoring and parameter adjustment, fracture propagation is effectively controlled, reducing the risk of roof instability and enhancing construction safety. This method is adaptable to different lithologies and aquifer (4) conditions at different burial depths, possessing strong universality and providing effective technical support for the prevention and control of water hazards in coal mine roofs.

[0024] In some embodiments, in step S1, the distance between the deep hole 2 and the shallow hole 3 is controlled to be 15m-30m; the depth of the shallow hole 3 is 10m-15m below the bottom plate of the aquifer 4.

[0025] The distance between deep borehole 2 and shallow borehole 3 is controlled between 15m and 30m. This spacing design aims to ensure that the fracture propagation range of adjacent boreholes can effectively overlap. Through the overlapping fracture propagation range, a continuous drainage network can be formed, enhancing the drainage effect. The depth of shallow borehole 3 is set to 10m to 15m below the bottom plate of aquifer 4. The purpose of setting shallow borehole 3 is to assist in connecting the fracture channel between aquifer 4 and deep borehole 2. This depth setting helps to prevent the problem of insufficient drainage from deep borehole 2 and provides assistance for the drainage of aquifer 4 through deep borehole 2. Specifically, the depth of deep borehole 2 is determined according to the burial depth of aquifer 4 (usually 50~100 meters); the depth of shallow borehole 3 is 20~50 meters (slightly deeper than the caving zone of the roof of coal seam 5).

[0026] By controlling the spacing between the shallow and deep boreholes (3), the continuity of fracture propagation and the integrity of the drainage network are ensured, thereby improving drainage efficiency. The placement of the shallow boreholes (3) and the assistance of the deep boreholes (2) enhance the drainage capacity of the deep boreholes (2), resolving the potential issue of insufficient drainage volume. The continuous drainage network and enhanced drainage capacity work together to significantly improve the drainage effect of aquifer 4. Precise control of borehole spacing and depth allows for more effective prediction and management of fracture propagation, reducing risks during construction. This design method is adaptable to different geological conditions, providing suitable borehole spacing and depth designs for different types of coal mines.

[0027] In some embodiments, in step S1, during drilling, the verticality of the borehole is ensured by using drilling-while-drilling inclination measurement technology; after drilling is completed, the sediment at the bottom of the borehole is flushed with high-pressure water with a pressure of ≥5MPa for a duration of ≥10min.

[0028] During drilling, measurement-while-drilling (MSD) technology is used to ensure the verticality of the borehole. This technology effectively avoids deviations caused by geological conditions or improper operation during drilling. By maintaining the verticality of the borehole, it is ensured that deep hole 2 can accurately enter aquifer 4, avoiding deviations that could prevent the desired drainage effect from being achieved.

[0029] After drilling is completed, the bottom of the borehole is flushed with high-pressure water at a pressure of ≥5MPa for at least 10 minutes. The purpose of this high-pressure water flushing is to remove sediment from the bottom of the borehole and ensure a clean borehole environment. A clean borehole environment is crucial for subsequent fracturing and fracturing agent injection, as it provides a good channel for the effective transfer of fluids and chemicals.

[0030] In some embodiments, step S2 specifically includes: Based on the depth of the deep hole 2, it is divided into 3-5 fracturing sections, each with a length of 6m-15m; A double-sealing perforator 9 is used to seal the upper and lower ends of the target fracturing section, forming a closed fracturing space; Fracturing is carried out by pumping clean water into the fracturing space using a high-pressure pump. The fracturing pressure is controlled at 25MPa-35MPa and maintained for 25min-35min. Following the sequence from the bottom of the borehole to the top, the sealing and fracturing operations were repeated for each fracturing section.

[0031] The deep borehole 2 fracturing section is divided into 3-5 sections based on its total depth, with each section ranging from 6m to 15m in length. The section length is adjusted according to the lithology of the aquifer 4: for sandstone aquifer 4, the section length can be appropriately increased; for mudstone aquifer 4, the section length can be shortened. A double-sealing perforator 9 is used to seal both ends of the target fracturing section, forming a closed fracturing space to ensure that the fracturing fluid only acts within the designated fracturing section.

[0032] Starting from the first fracturing section at the bottom of deep borehole 2, fracturing is gradually advanced towards the borehole opening. During each fracturing section, the sealing device 9 is first lowered into the upper and lower ends of the target fracturing section and expanded to form a closed fracturing space. Clean water is pumped into the fracturing space using a high-pressure pump to perform fracturing, with the fracturing pressure controlled between 25 MPa and 35 MPa, adjusted according to the lithology of aquifer 4. The fracturing pressure is maintained for 25 to 35 minutes until the hydraulically fracturing fracture 6 is fully expanded. After releasing the pressure, the sealing device 9 is moved to the next fracturing section. The above steps are repeated until all fracturing sections are completed.

[0033] Staged fracturing allows for more precise control of the fracturing process and improves fracturing efficiency. Adjusting the length of the fracturing stage according to different lithologies optimizes the fracturing effect and allows for more effective treatment of different types of aquifers. Staged fracturing reduces unnecessary waste of fracturing fluid and improves resource utilization. Using a perforator ensures that the fracturing fluid acts only in a designated area, minimizing the impact on the surrounding environment. Performing fracturing sequentially from the bottom of the borehole to the orifice ensures uniformity and consistency of fracturing.

[0034] In some embodiments, when dividing the fracturing sections, the section length is adjusted according to the lithology of aquifer 4: the section length is increased for sandstone aquifer 4 and shortened for mudstone aquifer 4. For sandstone aquifer 4, due to its relatively hard rock structure and relatively low degree of fracture development, the length of the fracturing section needs to be increased to increase the fracturing range and improve the uniformity and depth of fracture propagation. For mudstone aquifer 4, due to its relatively soft rock structure and high degree of fracture development, the natural extension of fractures is better, so the length of the fracturing section can be appropriately shortened to reduce the amount of fracturing work and improve construction efficiency.

[0035] In some embodiments, step S3 specifically includes: Insert the sealing device 9 20cm-35cm from the bottom of the shallow hole 3 and expand and fix it to form a closed fracturing space; Pump clean water into the fracturing space to perform fracturing at a pressure of 15MPa-25MPa for 15-25 minutes.

[0036] The perforator 9 is lowered into the shallow hole 3, positioned 20cm to 35cm from the bottom of the hole. The perforator 9 is then expanded to ensure it is fixed within the hole, thus forming a closed fracturing space. Clean water is pumped into the closed fracturing space using a high-pressure pump for fracturing. The fracturing pressure is controlled between 15MPa and 25MPa and maintained for 15 to 25 minutes to ensure effective fracturing.

[0037] By fixing the perforator 9 at a certain position from the bottom of the hole, the location of the fracturing action can be precisely controlled, preventing the fracturing fluid from spreading to unnecessary areas. The use of the perforator 9 ensures a closed fracturing space, allowing the fracturing fluid to concentrate on the target area and improving fracturing efficiency. The fracturing pressure can be adjusted according to the characteristics of the aquifer 4 to adapt to different lithologies and water-bearing conditions. Maintaining the fracturing pressure for a certain period ensures that the fracturing fluid has sufficient time to act on the rock, promoting fracture formation and propagation. Precise fracturing operations can reduce the impact of the fracturing fluid on the surrounding environment and improve construction safety. This method is adaptable to different types of aquifers 4, whether sandstone or mudstone, achieving optimal fracturing results by adjusting the fracturing pressure and time.

[0038] In some embodiments, in step S4, the method of injecting static cracking agent 7 is as follows: the static cracking agent 7 and water are stirred into a paste at a ratio of 1:0.3, and injected using a grouting pump at a pressure of 1MPa-2MPa, with an injection volume of 1.2-1.5 times the pore volume; after injection, wait 24h-48h for the cracking agent to fully react.

[0039] Static fracturing agent 7 is mixed with water at a ratio of 1:0.3 to form a paste. This mixing ratio ensures that the fracturing agent is evenly distributed during injection and reacts effectively in the rock. The mixed paste is injected into the borehole using a grouting pump at a pressure of 1 MPa to 2 MPa, with the injection volume controlled between 1.2 and 1.5 times the borehole volume to ensure sufficient fracturing agent to fill and expand the fractures. After injection, a waiting period of 24 to 48 hours is required to allow the fracturing agent to fully react within the borehole. This sufficient reaction time allows the fracturing agent to chemically react with the rock, effectively widening the fractures and improving permeability.

[0040] By injecting an appropriate amount of static fracturing agent 7, fractures can be effectively enlarged, rock permeability increased, and the release effect of aquifer 4 improved. A 1:0.3 mixing ratio ensures uniform distribution of the fracturing agent during injection, avoiding localized excessively high or low concentrations. An injection pressure of 1 MPa to 2 MPa ensures effective fracturing agent injection while avoiding potential borehole stability problems caused by excessively high pressure. A reaction time of 24 to 48 hours ensures sufficient time for the fracturing agent to react with the rock, achieving optimal fracturing effect. This method is relatively mild, reducing the risks associated with excessively high injection pressure or incomplete reaction.

[0041] In some embodiments, in step S5, the microseismic monitoring system includes a three-component microseismic sensor, a data acquisition instrument, and analysis software arranged in boreholes in the roof of the roadway within 20m around the borehole; the sensor is coupled to the surrounding rock with cement mortar, and the analysis software is used to calculate the location of microseismic events in real time to invert the fracture propagation range.

[0042] Three-component microseismic sensors are deployed in boreholes in the tunnel roof within a 20-meter radius of the borehole. These sensors record the motion of seismic waves in three vertical directions, providing comprehensive information about microseismic events such as crack propagation or rock fracturing. A data acquisition system collects data from the sensors, recording the captured microseismic signals in real time and ensuring the accuracy and completeness of the data. Analysis software processes and interprets the microseismic data, calculating the location of microseismic events in real time and inverting the extent and direction of crack propagation.

[0043] Specifically, the sensor is coupled to the surrounding rock via cement mortar to ensure it can effectively capture microseismic signals caused by fracture propagation or other geological activities. The data acquisition unit collects sensor data in real time, while the analysis software processes this data, including signal amplification, filtering, event identification, and location. Utilizing the principles of seismic wave propagation and combining sensor location information, the analysis software calculates the location of microseismic events in real time. By analyzing the location and timing of these microseismic events, the software can infer the extent and direction of fracture propagation, providing real-time feedback for fracturing operations.

[0044] Microseismic monitoring systems can monitor fracture propagation in real time, providing immediate data support for construction personnel. By accurately calculating the location of microseismic events, the extent of fracture propagation can be more precisely understood, thereby optimizing construction strategies. Real-time monitoring and precise location help to promptly detect and address potential geological risks, such as roof instability. Real-time feedback allows for timely adjustments to fracturing parameters, improving construction efficiency and reducing unnecessary repetitive work. Real-time monitoring and risk control help ensure safety during construction and reduce the likelihood of accidents.

[0045] In some embodiments, step S5, dynamically adjusting the fracturing construction parameters based on the microseismic monitoring results, includes: stopping fracturing when the fracture propagation range reaches the design requirements; increasing the fracturing pressure or displacement when the fracture propagation rate is slow; and reducing the fracturing pressure when the fracture propagation exceeds the design range.

[0046] When the fracture propagation reaches the design requirements, fracturing operations are stopped. This ensures that the operation proceeds according to the predetermined goals and scope, avoiding unnecessary waste of resources and potential safety risks. When monitoring results show that the fracture propagation rate is slow, the following measures can be taken: increasing the fracturing pressure can promote rapid fracture propagation; or increasing the injection volume of fracturing fluid can provide more fluid energy to drive fracture propagation.

[0047] When the fracture extends beyond the design range, measures need to be taken to control its further extension: reducing the fracturing pressure can slow down the fracture extension rate and prevent geological risks caused by excessive extension.

[0048] Real-time monitoring and adjustment ensure that construction proceeds according to plan, improving efficiency. Timely parameter adjustments when fracture propagation is slow or exceeds design limits control construction risks and prevents geological disasters caused by improper fracture propagation. Over-fracture is avoided, conserving fracturing fluid and other resources. Precise control of fracturing parameters reduces the impact on surrounding rock stability, enhancing construction safety. Dynamic parameter adjustments facilitate more precise fracture control, thereby improving drainage effectiveness and construction quality.

[0049] In some embodiments, deep holes 2 and shallow holes 3 work together to form a continuous drainage network for diverting water from the aquifer 4 along the expanded fracture network to the goaf 1.

[0050] Deep hole 2 penetrates the roof of coal seam 5 and enters the aquifer 4, forming the main drainage channel. Shallow hole 3 is located in the transition layer below aquifer 4, assisting deep hole 2 in draining water from aquifer 4. The coordinated design of deep hole 2 and shallow hole 3 ensures the continuity of the drainage network, allowing water in aquifer 4 to flow smoothly along the fracture network to goaf 1. Deep hole 2, as the main drainage channel, is responsible for a larger drainage volume; shallow hole 3, as an auxiliary channel, helps connect the fracture channel between aquifer 4 and deep hole 2, preventing insufficient drainage from deep hole 2.

[0051] A continuous drainage network can more effectively divert water from aquifer 4 to goaf 1, reducing the risk of water accumulation and improving drainage efficiency. The configuration of deep and shallow boreholes 3 can be adjusted according to different geological conditions and the characteristics of aquifer 4, enhancing the adaptability of the drainage network. By reducing the reliance on deep boreholes 2 for drainage, construction costs can be reduced, especially given the high difficulty and cost of constructing deep boreholes 2. Effective drainage can reduce the risk of geological disasters caused by water accumulation, such as roof collapse, thereby improving construction safety. Through a reasonable drainage network design, resource utilization can be optimized, reducing water waste.

[0052] This invention presents a microseismic-based fracturing borehole drainage method for aquifers in coal mine roofs. By innovatively employing a "coordinated deep and shallow borehole 3 hydraulic fracturing borehole drainage" process, it first solves the drainage problem caused by the limited drainage capacity of a single deep borehole 2 in traditional methods. The coordinated design of the deep and shallow boreholes 3 forms a continuous drainage network, allowing water in the aquifer 4 to flow more smoothly to the goaf 1 through the expanded fracture network. This invention introduces "retreating segmented fracturing" and "static fracturing agent 7 secondary permeability enhancement" technologies, further expanding the fracture range and increasing branch fractures, significantly improving the permeability coefficient of the aquifer 4 and effectively solving the problem of limited permeability improvement in traditional fracturing methods. To monitor fracture propagation in real time and dynamically adjust construction parameters, this invention also integrates a "microseismic real-time monitoring" system. This not only helps to accurately control fracture propagation but also significantly reduces the risk of roof instability, thereby improving construction safety.

[0053] Overall, this invention achieves efficient drainage of the aquifer 4 in the roof of coal mines through a combined process of "coordinated hydraulic fracturing drilling for drainage from deep and shallow boreholes + static fracturing for secondary permeability enhancement + real-time microseismic monitoring". This method not only solves the problems of low permeability coefficient, poor drainage effect, and difficulty in controlling fracture propagation in traditional drainage methods, but also has the advantages of high drainage efficiency, good safety, and strong adaptability, providing more effective technical support for the prevention and control of water hazards in the roof of coal mines.

[0054] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0055] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0056] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0057] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "beneath" of the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0058] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. 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.

[0059] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for draining aquifers from the roof of a coal mine using microseismic fracturing boreholes, characterized in that, Includes the following steps: S1. In the roof above the goaf of a coal mine, at least one deep hole and at least one shallow hole are constructed to form a drainage channel network covering the aquifer and transition layer; the end point of the deep hole penetrates the roof of the coal seam and enters the interior of the aquifer, and the end point of the shallow hole is located in the transition layer below the aquifer. S2. The deep hole is subjected to a backward segmented hydraulic fracturing process to form multiple hydraulic fracturing fractures inside the aquifer. S3. Perform a single hydraulic fracturing operation on the bottom of the shallow hole to form radial fractures within the transition layer; S4. Inject a static fracturing agent into the deep and shallow holes where hydraulic fracturing has been completed to expand the hydraulic fracturing fractures and form static fracturing fractures. S5. During the hydraulic fracturing process in steps S2 and S3, a microseismic monitoring system arranged around the borehole is used to monitor the fracture propagation range in real time, and the fracturing construction parameters are dynamically adjusted according to the monitoring results.

2. The method for draining aquifers from the roof of a coal mine based on microseismic fracturing boreholes according to claim 1, characterized in that, In step S1, the distance between the deep hole and the shallow hole is controlled between 15m and 30m; the depth of the shallow hole is 10m to 15m below the bottom plate of the aquifer.

3. The method for draining aquifers from the roof of a coal mine based on microseismic fracturing boreholes according to claim 1, characterized in that, In step S1, during drilling, the verticality of the borehole is ensured by using drilling-while-drilling inclination measurement technology; after drilling is completed, the sediment at the bottom of the borehole is flushed with high-pressure water with a pressure of ≥5MPa for a duration of ≥10min.

4. The method for draining aquifers from the roof of a coal mine based on microseismic fracturing boreholes according to claim 1, characterized in that, Step S2 specifically includes: Based on the depth of the deep hole, it is divided into 3-5 fracturing sections, each with a length of 6m-15m; A double-sealing perforator is used to seal the upper and lower ends of the target fracturing section, forming a closed fracturing space; Fracturing is performed by pumping clean water into the fracturing space using a high-pressure pump, with the fracturing pressure controlled at 25MPa-35MPa and maintained for 25min-35min. Following the sequence from the bottom of the borehole to the top, the sealing and fracturing operations were repeated for each fracturing section.

5. The method for draining aquifers from the roof of a coal mine based on microseismic fracturing boreholes according to claim 4, characterized in that, When dividing the fracturing sections, the section length is adjusted according to the lithology of the aquifer: the section length of sandstone aquifers is increased, and the section length of mudstone aquifers is shortened.

6. The method for draining aquifers from the roof of a coal mine based on microseismic fracturing boreholes according to claim 1, characterized in that, Step S3 specifically includes: The sealing device is inserted 20cm-35cm from the bottom of the shallow hole and expanded and fixed to form a closed fracturing space. Water is pumped into the fracturing space for fracturing at a pressure of 15MPa-25MPa for 15-25 minutes.

7. The method for draining aquifers from the roof of a coal mine based on microseismic fracturing boreholes according to claim 1, characterized in that, In step S4, the method for injecting the static cracking agent is as follows: the static cracking agent and water are stirred into a paste at a ratio of 1:0.3, and injected using a grouting pump at a pressure of 1MPa-2MPa. The injection volume is 1.2-1.5 times the pore volume. After injection, wait 24h-48h for the cracking agent to react fully.

8. The method for draining aquifers from the roof of a coal mine based on microseismic fracturing boreholes according to claim 1, characterized in that, In step S5, the microseismic monitoring system includes a three-component microseismic sensor, a data acquisition instrument, and analysis software arranged in boreholes in the roof of the roadway within 20m around the borehole; the sensor is coupled to the surrounding rock with cement mortar, and the analysis software is used to calculate the location of microseismic events in real time to invert the fracture propagation range.

9. The method for draining aquifers from the roof of a coal mine based on microseismic fracturing boreholes according to claim 1 or 8, characterized in that, In step S5, the fracturing operation parameters are dynamically adjusted based on the microseismic monitoring results, including: stopping fracturing when the fracture propagation range reaches the design requirements; increasing the fracturing pressure or displacement when the fracture propagation rate is slow; and reducing the fracturing pressure when the fracture propagation exceeds the design range.

10. The method according to claim 1, characterized in that, The deep and shallow holes work together to form a continuous drainage network, which is used to guide the aquifer water along the expanded fracture network to the goaf.

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