A method and system for high-temperature steam fracturing of coal measures in mountainous regions

Abstract

The present application relates to the technical field of tunnel construction, in particular to a high-temperature steam fracturing method and system for coal measures strata in mountainous areas, which realizes continuous and real-time monitoring of the spatio-temporal evolution of the temperature field in the fracturing process through distributed optical fiber temperature sensing technology, captures microseismic signals generated by fracturing through distributed optical fiber acoustic sensing technology, obtains underground apparent shear wave velocity profile imaging, and performs multi-parameter collaborative analysis and fusion of the temperature field evolution, spatial distribution of microseismic events, and apparent shear wave velocity profile changes before and after fracturing, thereby realizing comprehensive and accurate delineation of the influence range of hot steam fracturing; the fracturing system, based on the high-temperature steam fracturing method for coal measures strata in mountainous areas, has a simple structure and is easy to arrange, and can accurately characterize the fracturing effect under the thermal-mechanical coupling effect in the hot steam fracturing process in real time, thereby providing an effective means for optimizing gas extraction from coal measures strata in mountainous areas and ensuring tunnel construction safety.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, specifically to a method and system for high-temperature steam fracturing in coal-bearing strata in mountainous areas. Background Technology

[0002] Mountain tunnel projects often traverse coal-bearing strata with extremely complex geological conditions. These strata are generally characterized by high gas content and weak, fractured rock masses, significantly increasing construction difficulty and posing serious threats to construction safety, such as gas outbursts and surrounding rock instability. Hot steam fracturing technology, as an effective means of enhancing gas drainage, significantly improves the permeability of coal seams by injecting high-temperature steam, promoting gas desorption and migration, and thus increasing gas drainage efficiency. This provides crucial assurance for the safe passage of tunnels through high-gas coal seam areas.

[0003] However, in the practice of hot steam fracturing in existing tunnel engineering, there is a lack of effective monitoring methods that can accurately characterize the crack propagation morphology and influence range under thermo-mechanical coupling in real time. It is difficult to obtain the temperature field distribution and crack dynamic evolution information during the fracturing process simultaneously, which leads to uncertainty in the determination of the influence range of the fracturing area, affecting the application effect of hot steam fracturing, the optimization of gas extraction schemes, and the precise control of construction safety risks. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies, such as the difficulty in simultaneously obtaining temperature field distribution and crack dynamic evolution information during the fracturing process in existing tunnel engineering, which affects the application effect of hot steam fracturing, the optimization of gas extraction schemes, and the precise control of construction safety risks. This invention provides a method and system for high-temperature steam fracturing in coal-bearing strata in mountainous areas.

[0005] In a first aspect, the present invention provides a method for high-temperature steam fracturing of coal-bearing strata in mountainous areas, comprising the following steps: S1. Set up a temperature monitoring system and a vibration signal monitoring system. The temperature monitoring system includes a distributed fiber optic temperature sensor, and the vibration signal monitoring system includes a distributed fiber optic acoustic sensor. S2. Obtain the apparent shear wave velocity profile image of the tunnel coal seam area before hot steam fracturing. S3. Drill saturated steam into the tunnel face to heat and fracture the coal seam; simultaneously acquire coal seam temperature and fracture vibration signals to determine the distribution location of microseismic events in the fractured area; S4. Stop the hot steam fracturing. Combine the coal seam temperature distribution and changes, the distribution density of microseismic events, and the changes in the apparent shear wave velocity profile imaging of the tunnel coal seam area before and after fracturing to comprehensively determine the fracturing influence range of hot steam injection. S5. Extract gas and analyze the fracturing effect. If the fracturing effect does not meet expectations, repeat steps S2-S4 until the gas extraction effect meets the standard.

[0006] Preferably, in step S1, temperature measurement holes are drilled in the tunnel face of the excavated section of the tunnel, directly ahead of the unexcavated section of the tunnel, through the coal-bearing strata. Temperature-measuring armored optical fibers are installed within these holes and connected to a DTS demodulator, forming a temperature monitoring system. The DTS demodulator analyzes the backscattered Raman light signal in the optical fiber in real time, obtaining the temperature signals at various measurement points along the optical fiber based on Raman time-domain reflectometry.

[0007] Preferably, it includes three temperature measuring holes, which are distributed in an isosceles triangle on the top side and the lateral sides of the working face. Each temperature measuring hole is equipped with a temperature measuring armored optical fiber and sealed with cement mortar.

[0008] Preferably, in step S1, a pressure-measuring armored optical fiber is buried along the slope at the top of the mountain in the tunnel area and connected to a DAS demodulator to form a vibration signal monitoring system. The DAS demodulator is placed at the top of the mountain. The DAS demodulator obtains the vibration signals at each measuring point along the optical fiber by analyzing the backscattered Rayleigh light signal in the optical fiber in real time, based on phase-sensitive optical time-domain reflectometry.

[0009] Preferably, S2 includes: S2.1 Obtain vibration signals in the coal seam area of ​​the tunnel through a vibration signal monitoring system; S2.2 Obtain the dispersion curve of the surface wave component in the vibration signal using the spatial autocorrelation method; S2.3. The apparent shear wave velocity profile of the tunnel coal seam region is obtained by analyzing the dispersion information obtained from the dispersion curve.

[0010] Preferably, in S3, a hot steam fracturing hole is drilled directly forward from the middle of the tunnel face. The hot steam fracturing hole is located between the temperature measuring holes, and the depth of the hot steam fracturing hole exceeds the coal outlet point of the borehole by more than 1m.

[0011] Preferably, in S3, determining the distribution location of microseismic events in the fracturing zone includes: S3.1 Preprocess the fracture vibration signal to obtain the target signal; S3.2 Identifying microseismic events in target signals based on long and short time window algorithms; S3.3. The time of the first identified microseismic event is determined as the first arrival time of the P-wave; S3.4. Combine the initial arrival time of the longitudinal wave with the time difference inversion positioning algorithm to determine the distribution location of microseismic events in the fracturing area.

[0012] Preferably, in S4, the distribution density of microseismic events is determined based on the distribution location of microseismic events in the fracturing area obtained in S3.

[0013] Preferably, in S4, after injecting saturated steam to heat and fracturing the coal seam for 2-4 hours, the steam fracturing is stopped and the borehole is sealed.

[0014] In a second aspect, the present invention provides a high-temperature steam fracturing system for coal-bearing formations in mountainous areas, employing a high-temperature steam fracturing method for coal-bearing formations in mountainous areas as described above, including a hot steam fracturing system, a temperature monitoring system, and a vibration signal monitoring system. The hot steam fracturing system and the temperature monitoring system are installed inside the tunnel, while the vibration signal monitoring system is installed on the top of the mountain where the tunnel is located.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a method for high-temperature steam injection fracturing in coal-bearing formations in mountainous areas. It achieves continuous and real-time monitoring of the spatiotemporal evolution of the temperature field during fracturing through distributed fiber optic temperature sensing technology, and captures microseismic signals generated by fracturing through distributed fiber optic acoustic sensing technology to obtain subsurface apparent shear wave velocity profile imaging. It performs multi-parameter collaborative analysis and fusion of temperature field evolution, spatial distribution of microseismic events, and changes in apparent shear wave velocity profile before and after fracturing to achieve comprehensive and accurate delineation of the influence range of hot steam injection fracturing. 2. This invention provides a high-temperature steam fracturing system for coal-bearing formations in mountainous areas. Based on a high-temperature steam fracturing method for coal-bearing formations in mountainous areas, it has a simple structure and is easy to set up. It can accurately characterize the fracturing effect under the thermo-mechanical coupling effect during the hot steam fracturing process in real time, providing an effective means to optimize gas extraction in coal-bearing formations in mountainous areas and ensure the safety of tunnel construction. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a high-temperature steam fracturing method for coal-bearing strata in mountainous areas, as shown in Example 1.

[0017] Figure 2 This is a schematic diagram showing the arrangement of the temperature measuring holes and the hot steam fracturing holes at the working face in Example 1.

[0018] Figure 3 This is a side view of a high-temperature steam fracturing system for coal-bearing formations in mountainous areas, as described in Example 2.

[0019] Figure 4 for Figure 3 A magnified schematic diagram of a portion of point A in the middle.

[0020] Figure 5 for Figure 3 A magnified schematic diagram of a portion of point B in the middle.

[0021] Figure 6 This is a schematic diagram of the layout of the steam fracturing system described in Example 2 in a tunnel.

[0022] Marked in the image: 1-Temperature monitoring system; 11-Temperature measuring armored fiber optic cable; 12-DTS demodulator; 2-Vibration signal monitoring system; 21-Pressure measuring armored fiber optic cable; 22-DAS demodulator; 3-Excavated part of the tunnel; 4-Unexcavated part of the tunnel; 5-Temperature measuring hole; 6-Hot steam fracturing hole; 7-Mountain body; 71-Coal-bearing strata; 8-Hot steam fracturing system; 81-Water storage mechanism; 82-Water pump; 83-Steam generator; 84-One-way valve. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0024] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, and for enabling those skilled in the art to quickly understand the solution. They do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship, and therefore should not be construed as limiting the present invention.

[0025] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," "parallel," and "coaxial" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, parallel, or coaxial. Slight tilt or deviation is permissible, as long as it does not affect the normal function of the relevant component. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," not that the structure must be perfectly horizontal; a slight tilt is acceptable. "Coaxial" means that two components are arranged as coaxially as possible, allowing them to move coaxially or approximately coaxially when their relative positions change. Alternatively, it can be simplified to mean that the corresponding device / component / element, when arranged in "horizontal," "vertical," "suspended," "parallel," or "coaxial" directions, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. For example, the deviation in the "coaxial" direction is controlled within 0.2-1mm, preferably within 0.2-0.5mm. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the solution of the present invention.

[0026] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0027] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as two, three, four, five, six, seven, eight, or nine, and can even exceed nine.

[0028] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to connection methods commonly used in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0029] Example 1 like Figures 1-6 As shown, a method for high-temperature steam fracturing in coal-bearing formations in mountainous areas includes the following steps: S1. Set up a temperature monitoring system 1 and a vibration signal monitoring system 2. The temperature monitoring system 1 includes a distributed optical fiber temperature sensor, and the vibration signal monitoring system 2 includes a distributed optical fiber acoustic sensor.

[0030] In an optional implementation, in step S1, a temperature measuring hole 5 is drilled at the face of the excavated section 3 of the tunnel directly ahead, through the coal-bearing strata 71 that the unexcavated section 4 of the tunnel needs to traverse. A temperature-measuring armored optical fiber 11 is installed in the temperature measuring hole 5 and connected to a DTS demodulator 12, forming a temperature monitoring system 1. The temperature monitoring system is based on distributed optical fiber temperature sensing technology. The DTS demodulator 12 analyzes the backscattered Raman light signal in the optical fiber in real time and obtains the temperature signal at each measuring point along the optical fiber based on Raman time-domain reflectometry (RTDR). This allows for real-time monitoring of the temperature field distribution and evolution of the coal-bearing strata 71 based on the ROTDR principle.

[0031] In an optional embodiment, the temperature-sensing armored fiber 11 can be coupled to the sidewall of the temperature-sensing hole 5 in the coal-bearing stratum 71. One end of the temperature-sensing armored fiber 11 can extend into the bottom of the borehole, and the other end can be connected to the DTS demodulator 12 arranged in the tunnel. The DTS demodulator 12 has four channels and can monitor the temperature of each measuring point along the fiber in real time.

[0032] In an optional embodiment, the face of the excavated portion 3 of the tunnel is close to the exposed surface of the coal-bearing strata 71.

[0033] In an optional embodiment, three temperature measuring holes 5 are included. The three temperature measuring holes 5 are distributed in an isosceles triangle on the top side and the transverse sides of the working face. Each temperature measuring hole 5 is equipped with a temperature measuring armored optical fiber 11 and sealed with cement mortar. The temperature measuring armored optical fiber 11 in the three temperature measuring holes 5 can be connected to a DTS demodulator 12.

[0034] In an optional implementation, in S1, a pressure-measuring armored optical fiber 21 is buried along the slope of the mountain 7 in the tunnel area and connected to a DAS demodulator 22 to form a vibration signal monitoring system 2. The DAS demodulator 22 is placed on the top of the mountain 7. The vibration signal monitoring system 2 is based on distributed optical fiber acoustic wave sensing technology. The DAS demodulator 22 analyzes the backscattered Rayleigh light signal in the optical fiber in real time and obtains the vibration signal at each measuring point along the optical fiber based on phase-sensitive optical time-domain reflectometry. It can collect background noise in real time based on the Φ-OTDR (phase-sensitive optical time-domain reflectometry) principle as the vibration signal, and obtain the underground apparent shear wave velocity profile of the fracturing area through SPAC (spatial autocorrelation method), providing a basis for judging the dynamic propagation information of the fracturing fracture.

[0035] In an optional implementation, a trench with a depth of 0.1-0.3m can be excavated on the top surface of the mountain 7 where the tunnel is located, and the pressure-measuring armored fiber 21 can be laid in the trench. The trench can then be buried to realize the installation of the pressure-measuring armored fiber 21. One end of the pressure-measuring armored fiber 21 is connected to the DAS demodulator 22 placed on the mountain top, which can monitor the vibration signal of each measuring point along the fiber in real time.

[0036] In an optional implementation, the pressure-measuring armored fiber optic cable 21 can be laid along the longitudinal direction of the tunnel.

[0037] S2. Obtain the apparent shear wave velocity profile image of the tunnel coal seam area before hot steam fracturing. The apparent shear wave velocity profile image of the tunnel coal seam area is obtained by analyzing the vibration signal near the coal-bearing strata 71 in the mountainous area acquired by the vibration signal monitoring system 2.

[0038] Specifically, S2 includes: S2.1. Obtain vibration signals in the coal seam area of ​​the tunnel through vibration signal monitoring system 2; S2.2 Obtain the dispersion curve of the surface wave component in the vibration signal using the spatial autocorrelation method; S2.3. The apparent shear wave velocity profile of the tunnel coal seam region is obtained by analyzing the dispersion information obtained from the dispersion curve.

[0039] It should be noted that the vibration signal acquired by the vibration signal monitoring system 2 is a micro-motion signal of the shallow surface of the earth, which is a complex vibration composed of body waves (P waves and S waves) and surface waves (Rayleigh waves and Love waves). The energy of the surface waves accounts for more than 70% of the total energy of the signal. Surface waves have a dispersion effect, and their dispersion characteristics carry rich information about the underground structure. By using the SPAC (spatial autocorrelation method), the dispersion curve of the surface wave component in the vibration signal can be obtained. Then, by using the corresponding dispersion information, the image of the apparent shear wave velocity profile of the underground geological structure in this area can be obtained.

[0040] S3. Drill saturated steam into the tunnel face to heat and fracture the coal seam; simultaneously acquire coal seam temperature and fracture vibration signals to determine the distribution location of microseismic events in the fractured area.

[0041] In an optional embodiment, in S3, a hot steam fracturing hole 6 is drilled directly forward from the center of the tunnel face. The hot steam fracturing hole 6 is located between the temperature measuring holes 5. The hot steam fracturing hole 6 can be located between the temperature measuring holes 5 on both sides of the tunnel. During the drilling process, attention should be paid to observing the drilling status, including feed force, pull-out force, drilling speed, rotation speed, pump flow rate, and drill bit jamming, as well as the drill cuttings condition, including the amount and properties of drill cuttings, to ensure the accuracy of the drilling depth and the safety of the drilling operation.

[0042] In an optional embodiment, during the drilling process, the hot steam fracturing hole 6 is formed by accurately recording the coal-encounter point, coal penetration length and coal exit point, drilling to the coal exit point and then drilling 1m further into the rock strata in front of the coal seam and then retracting the drill bit, so that the depth of the hot steam fracturing hole 6 exceeds the coal exit point of the borehole by more than 1m, in order to meet the hot steam fracturing operation.

[0043] In an optional embodiment, in S3, saturated steam is injected into the hot steam fracturing hole 6 via a hot steam fracturing system to perform hot steam fracturing operations. The hot steam fracturing system 8 includes a water storage mechanism 81, a water pump 82, and a steam generator 83 connected by pipelines. The steam generator 83 is connected to the hot steam fracturing hole 6 via pipelines. The hot steam fracturing system 8 can be arranged in the tunnel. By starting the water pump 82 and the steam generator 83, water in the water storage mechanism 81 is pumped into the steam generator 83 through the water pump 82, generating saturated steam at 250~300℃ and a pressure of 4~8.7MPa. The saturated steam flows into the hot steam fracturing hole 6 through a one-way valve 84, increasing the gas pressure inside the hole, applying pressure to the hole wall, heating and fracturing the coal-bearing strata 71, causing the temperature of the coal-bearing strata 71 to rise and generate fracturing fractures.

[0044] In an optional implementation, in step S3, determining the distribution location of microseismic events in the fracturing zone includes: S3.1 Preprocess the fracture vibration signal to obtain the target signal; S3.2 Identifying microseismic events in target signals based on long and short time window algorithms; S3.3. The time of the first identified microseismic event is determined as the first arrival time of the P-wave; S3.4. Combine the initial arrival time of the longitudinal wave with the time difference inversion positioning algorithm to determine the distribution location of microseismic events in the fracturing area.

[0045] S4. Stop the hot steam fracturing. Combine the coal seam temperature distribution and changes, the distribution density of microseismic events, and the changes in the apparent shear wave velocity profile of the tunnel coal seam area before and after fracturing to comprehensively determine the fracturing influence range of hot steam injection.

[0046] Specifically, the coal seam temperature distribution and changes are obtained through real-time monitoring by the temperature monitoring system. The distribution density of microseismic events is determined based on S3 to determine the distribution location of microseismic events in the fracturing area. The changes in the apparent shear wave velocity profile of the coal seam area before and after fracturing are obtained through vibration signal analysis obtained by the vibration signal monitoring system 2. By comprehensively determining the fracturing influence range of the injected steam through the temperature distribution and changes, the distribution density of microseismic events, and the changes in the apparent shear wave velocity profile of the coal seam area before and after fracturing, the fracturing effect of the high-temperature steam fracturing process under the thermo-mechanical coupling effect can be characterized in real time and accurately.

[0047] In an optional implementation, in S4, after injecting saturated steam to heat and fracture the coal seam for 2-4 hours, the operation of the water pump 82 and the steam generator 83 is stopped, the one-way valve 84 is closed, the steam injection is stopped, and the hot steam fracturing hole 6 is sealed to achieve the purpose of increasing gas production.

[0048] S5. Extract gas and analyze the fracturing effect. If the fracturing effect does not meet expectations, repeat steps S2-S4 until the gas extraction effect meets the standard.

[0049] In an optional implementation, in step S5, after removing the sealing structure of the hot steam fracturing hole 6, gas extraction is carried out, and the fracturing effect is judged based on the extraction results. If the fracturing effect does not meet the requirements or does not meet the expectations, steps S2-S4 are repeated until the gas extraction effect meets the standards, and then the coal seam permeability enhancement and gas extraction work in this area is completed.

[0050] This embodiment presents a high-temperature steam fracturing method for coal-bearing strata in mountainous areas. It utilizes distributed fiber optic temperature sensing technology to achieve continuous and real-time monitoring of the spatiotemporal evolution of the temperature field during fracturing, enabling monitoring of coal seam temperature distribution. Distributed fiber optic acoustic sensing technology captures microseismic signals generated by fracturing. The method employs spatial autocorrelation to obtain subsurface apparent shear wave velocity profile imaging, achieving pre-fracturing background noise surface wave imaging, fracturing time-seismic location during fracturing, and post-fracturing background noise surface wave imaging. By performing multi-parameter collaborative analysis and fusion of temperature field evolution, spatial distribution of microseismic events, and changes in apparent shear wave velocity profiles before and after fracturing, it achieves comprehensive and precise delineation of the influence range of steam fracturing. This method can accurately characterize the fracturing effect under thermo-mechanical coupling during high-temperature steam fracturing in real time, providing an effective means to optimize gas extraction in coal-bearing strata in mountainous areas and ensure tunnel construction safety.

[0051] Example 2 like Figures 2-6 As shown, a high-temperature steam fracturing system for coal-bearing formations in mountainous areas adopts the high-temperature steam fracturing method for coal-bearing formations in mountainous areas described in Example 1. It includes a hot steam fracturing system 8, a temperature monitoring system 1, and a vibration signal monitoring system 2. The hot steam fracturing system 8 and the temperature monitoring system 1 are installed inside the tunnel, and the vibration signal monitoring system 2 is installed on the top of the mountain 7 where the tunnel is located.

[0052] The hot steam fracturing system 8 includes a water storage mechanism 81, a water pump 82, and a steam generator 83 connected by pipelines. The steam generator 83 is connected to the hot steam fracturing hole 6 by pipelines, and a one-way valve 84 is installed in front of the hot steam fracturing hole 6.

[0053] The temperature monitoring system 1 is formed by drilling temperature measuring holes 5 in the working face of the excavated part 3 of the tunnel, directly in front of the unexcavated part 4 of the tunnel, through the coal-bearing strata 71, and laying temperature measuring armored optical fibers 11 in the temperature measuring holes 5 and connecting them to the DTS demodulator 12 in the tunnel.

[0054] The vibration signal monitoring system 2 is formed by excavating a trench with a depth of 0.1-0.3m on the top surface of the mountain 7 where the tunnel is located, laying the pressure-measuring armored fiber 21 in the trench, and then burying the trench to achieve the burial of the pressure-measuring armored fiber 21. One end of the pressure-measuring armored fiber 21 is connected to the DAS demodulator 22 placed on the top of the mountain.

[0055] This embodiment of a high-temperature steam injection fracturing system for coal-bearing formations in mountainous areas has a simple structure and is easy to deploy. Based on the high-temperature steam injection fracturing method for coal-bearing formations in mountainous areas in Embodiment 1, it can accurately characterize the fracturing effect under the thermo-mechanical coupling effect during the hot steam injection fracturing process in real time, providing an effective means to optimize the extraction of 71 gas from coal-bearing formations in mountainous areas and ensure the safety of tunnel construction.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for high-temperature steam fracturing in coal-bearing strata in mountainous areas, characterized in that, Includes the following steps: S1. Set up a temperature monitoring system (1) and a vibration signal monitoring system (2). The temperature monitoring system (1) includes a distributed optical fiber temperature sensor, and the vibration signal monitoring system (2) includes a distributed optical fiber acoustic sensor. S2. Obtain the apparent shear wave velocity profile image of the tunnel coal seam area before hot steam fracturing. S3. Drill saturated steam into the tunnel face to heat and fracture the coal seam; simultaneously acquire coal seam temperature and fracture vibration signals to determine the distribution location of microseismic events in the fractured area; S4. Stop the hot steam fracturing. Combine the coal seam temperature distribution and changes, the distribution density of microseismic events, and the changes in the apparent shear wave velocity profile imaging of the tunnel coal seam area before and after fracturing to comprehensively determine the fracturing influence range of hot steam injection. S5. Extract gas and analyze the fracturing effect. If the fracturing effect does not meet expectations, repeat steps S2-S4 until the gas extraction effect meets the standard. In S1, three temperature measuring holes (5) are drilled in the coal-bearing strata (71) that the excavated part (3) of the tunnel faces directly ahead and the unexcavated part (4) of the tunnel needs to pass through. Temperature measuring armored optical fibers (11) are laid in the temperature measuring holes (5) and connected to the DTS demodulator (12) to form a temperature monitoring system (1). It includes three temperature measuring holes (5), which are distributed in an isosceles triangle on the top side and the transverse sides of the working face. Each temperature measuring hole (5) is equipped with a temperature measuring armored optical fiber (11) and sealed with cement mortar. In S1, pressure-measuring armored optical fiber (21) is buried along the slope of the top of the mountain (7) in the tunnel area and connected to the DAS demodulator (22) to form a vibration signal monitoring system (2). The DAS demodulator (22) is placed on the top of the mountain (7).

2. The method for high-temperature steam fracturing in coal-bearing strata in mountainous areas according to claim 1, characterized in that, S2 include: S2.

1. Vibration signals in the coal seam area of ​​the tunnel are obtained through a vibration signal monitoring system (2); S2.2 Obtain the dispersion curve of the surface wave component in the vibration signal using the spatial autocorrelation method; S2.

3. The apparent shear wave velocity profile of the tunnel coal seam region is obtained by analyzing the dispersion information obtained from the dispersion curve.

3. The method for high-temperature steam fracturing in mountainous coal-bearing strata according to claim 1, characterized in that, In S3, a hot steam fracturing hole (6) is drilled directly forward from the middle of the tunnel face. The hot steam fracturing hole (6) is set between the temperature measuring holes (5). The depth of the hot steam fracturing hole (6) exceeds the coal outlet point of the borehole by more than 1m.

4. The method for high-temperature steam fracturing in coal-bearing strata in mountainous areas according to claim 3, characterized in that, In S3, determining the distribution location of microseismic events in the fracturing zone includes: S3.1 Preprocess the fracture vibration signal to obtain the target signal; S3.2 Identifying microseismic events in target signals based on long and short time window algorithms; S3.

3. The time of the first identified microseismic event is determined as the first arrival time of the P-wave; S3.

4. Combine the initial arrival time of the longitudinal wave with the time difference inversion positioning algorithm to determine the distribution location of microseismic events in the fracturing area.

5. A method for high-temperature steam fracturing in coal-bearing strata in mountainous areas according to claim 4, characterized in that, In S4, the distribution density of microseismic events is determined based on the distribution location of microseismic events in the fracturing region obtained in S3.

6. The method for high-temperature steam fracturing in coal-bearing strata in mountainous areas according to claim 3, characterized in that, In S4, after injecting saturated steam to heat and fracturing the coal seam for 2-4 hours, the steam injection for fracturing is stopped and the borehole is sealed.

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