A method for arranging microseismic monitoring sensors suitable for hydraulic fracturing of coal seam roof

Abstract

This invention relates to a method for arranging microseismic monitoring sensors for hydraulic fracturing of coal seam roofs, belonging to the field of coal mining technology. Specifically, it includes the following steps: S1: Drilling a long borehole from one side of the auxiliary haulage roadway toward the belt conveyor roadway on the roof of the auxiliary haulage roadway; drilling a short borehole perpendicular to the auxiliary haulage roadway on the rock wall between the auxiliary haulage roadway and the belt conveyor roadway; placing sensors at the bottom of the boreholes; S2: In the next connecting roadway, drilling a long borehole perpendicular to the working face advance direction on the rock wall between the auxiliary haulage roadway and the belt conveyor roadway; drilling a short borehole perpendicular to the auxiliary haulage roadway on the rock wall between the auxiliary haulage roadway and the belt conveyor roadway; placing sensors at the bottom of the boreholes; S3: Repeating steps S1 to S2 as the roadway advances. This invention achieves effective capture of micro-fracture signal sources in the coal seam roof during hydraulic fracturing, improving the positioning accuracy of the microseismic source.

Description

Technical Field

[0001] This invention belongs to the field of coal mining technology, and in particular relates to a method for arranging microseismic monitoring sensors suitable for hydraulic fracturing of coal seam roof. Background Technology

[0002] As coal resources are mined at greater depths, deep mine pressure has gradually become one of the major hazards affecting safe production in mines. During underground coal seam mining, the overlying strata continuously undergo activities such as caving, bending, sliding, and fracturing as the coal face advances, causing continuous changes in energy and stress in the mining area. These changes ultimately manifest as stress on the working face supports, deformation of the surrounding rock, and failure of the support structure, easily leading to dynamic disasters in the mine. To pre-control and prevent such risks, it is necessary to pre-treat the thick, hard roof of the roadway. In coal mining, directional long-hole hydraulic fracturing is often used to disrupt the integrity of the roof, reduce stress concentration, and lower the risk of sudden roof collapse. Because traditional techniques struggle to directly detect subtle pressure changes, research on the roof activity patterns under hydraulic fracturing is relatively limited. Compared to traditional physical observation methods, microseismic monitoring technology can more precisely observe the minute changes in roof activity after hydraulic fracturing. Research on the roof movement patterns under directional long-bore hydraulic fracturing based on microseismic events is of great significance for the safe and efficient mining of coal mines.

[0003] Microseismic monitoring technology, as a three-dimensional regional vibration wave monitoring method, utilizes the acoustic emission phenomenon caused by rock fracturing after hydraulic fracturing in the monitored area. Sensors are deployed to capture the microseismic signals generated during fracturing, and these signals are then converted into digital signals for recording and analysis using high-precision instruments. Its advantages lie in its high sensitivity, high resolution, and real-time performance. By monitoring and analyzing minute vibration signals, it can provide accurate information on the location and scale of hydraulic fracturing activities, providing strong support for the safe management of roof pressure in coal mines and feasibility studies on releasing stress concentration in coal seam roofs through hydraulic fracturing.

[0004] Chinese Patent (Publication No.: CN118191967A, Publication Date: June 14, 2024) discloses a three-dimensional intelligent early warning system and method for full-space monitoring of coal seam roof water hazard risk, including a hydrological monitoring subsystem, a microseismic monitoring subsystem, a continuous electrical resistivity tomography (TEM) monitoring subsystem, a database server, a data processing center, and a roof water hazard monitoring and early warning platform. Based on a static assessment of coal seam roof water hazard risk, it integrates the data interpretation and processing results from hydrological monitoring, microseismic monitoring, and TEM monitoring to provide early warning of coal seam roof water hazard. This invention integrates the hydrological monitoring subsystem, microseismic monitoring subsystem, TEM monitoring subsystem, water hazard risk assessment subsystem, and water hazard early warning subsystem, providing more comprehensive monitoring data. It constructs an IHHO-Att-LSTM intelligent early warning model for water hazard risk levels, enabling real-time intelligent early warning of coal seam roof water hazard risk with higher accuracy. However, the directional long boreholes drilled during roof monitoring are technically challenging to implement, as the borehole position and direction cannot be precisely located, resulting in inaccurate distance calculations for positioning accuracy.

[0005] Due to limitations in sensor placement along the tunnel's orientation, installation height and location cannot follow traditional methods. Conventional underground roof monitoring typically places microseismic sensors diagonally above or at a certain distance above the tunnel walls. However, because hydraulic fracturing signals are weak and have short propagation distances, and for drilling sites where the highest borehole is positioned high above the tunnel surface, conventional placement methods are inaccurate and do not meet monitoring requirements. Therefore, conventional sensor placement methods cannot be used for hydraulic fracturing roof monitoring, necessitating a new sensor placement approach. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for arranging microseismic monitoring sensors suitable for hydraulic fracturing of coal seam roofs.

[0007] A method for arranging microseismic monitoring sensors suitable for hydraulic fracturing of coal seam roofs, specifically including the following steps:

[0008] S1: The first set of sensors is arranged in the first connecting auxiliary transport roadway (17) and the belt transport roadway (16).

[0009] S1.1: On the top plate of the auxiliary transport roadway (17), a long borehole is drilled from one side of the auxiliary transport roadway (17) toward the belt transport roadway (16). The entire long borehole is on one side of the hydraulic fracturing borehole and forms an angle with the auxiliary transport roadway (17). Sensor I (1) is arranged at the bottom of the long borehole.

[0010] S1.2: Drill a short borehole perpendicular to the direction of the auxiliary transport roadway (17) on the rock wall between the auxiliary transport roadway (17) and the conveyor belt transport roadway (16), and place sensor Ⅲ (3) at the bottom of the short borehole;

[0011] S2: Along the working face advance direction, deploy the second set of sensors in the next connecting auxiliary transport roadway (17) and belt transport roadway (16).

[0012] S2.1: Drill a long borehole in the rock wall between the auxiliary transport roadway (17) and the conveyor belt transport roadway (16), perpendicular to the direction of the auxiliary transport roadway (17). The long borehole passes through the midpoint of the line connecting the centers of the two hydraulic fracturing boreholes below. Place sensor II (2) at the bottom of the long borehole.

[0013] S2.2: Drill a short borehole perpendicular to the auxiliary transport roadway (17) on the rock wall between the auxiliary transport roadway (17) and the conveyor belt transport roadway (16), and place sensor Ⅳ (4) at the bottom of the short borehole;

[0014] S3: As the tunnel advances, repeat steps S1 to S2, alternating between the first and second sets of sensors.

[0015] In step S1.1, sensor I (1) is in a direction with an inclination angle of 75° perpendicular to the roadway advance direction, at an angle of 63° to the working face advance direction, and at an angle of 60° to the horizontal projection of the long borehole, with a borehole length of 73.4m.

[0016] In step S1.2, sensor III (3) is located directly above the conveyor belt transport roadway (16) and the auxiliary transport roadway (17) at an angle of 38° perpendicular to the roadway advance direction, with a borehole length of 4.5m.

[0017] In step S2.1, sensor II (2) is located directly above the conveyor belt roadway (16) at an angle of 54° perpendicular to the roadway's advancing direction, with a borehole length of 80.3m.

[0018] In step S2.2, sensor IV (4) is located directly above the conveyor belt roadway (16) at an angle of 45° perpendicular to the roadway's advancing direction, with a borehole length of 4.5m.

[0019] The long and short drill holes in steps S1 and S2 have different angles and directions, and the sensors arranged in the long and short drill holes are staggered in the vertical projection.

[0020] The sensors used in this method are all velocity sensors.

[0021] In step S1, the sensor installed in the long borehole is 12m away from the center of the nearest hydraulic fracturing borehole. The long boreholes drilled when the first set of sensors is arranged and the long boreholes drilled when the second set of sensors is arranged are both at the same height as the hydraulic fracturing borehole farthest from the roadway. The short boreholes drilled when the first set of sensors is arranged and the short boreholes drilled when the second set of sensors is arranged are both 26.5m away from the center of the nearest hydraulic fracturing borehole.

[0022] The beneficial effects of the present invention are:

[0023] This invention provides a method for arranging microseismic monitoring sensors suitable for hydraulic fracturing of coal seam roofs. Sensors are arranged on the roof of auxiliary transport roadways and belt conveyor roadways. In each sensor arrangement, long and short boreholes are drilled, and this enveloping arrangement of long and short boreholes improves measurement accuracy. Sensors in the long and short boreholes can simultaneously measure microseismic events generated by hydraulic fracturing at different depths. By comparing the measurement results from the long and short boreholes, the location and magnitude of microseismic events can be observed more accurately and comprehensively. This improves measurement accuracy while cross-validating the results, reducing the probability of measurement errors due to single sensor failure, and allows for simultaneous measurements at multiple locations, improving measurement efficiency. This can save time and labor costs for projects requiring a large number of measurement points, such as enveloping boreholes.

[0024] This invention establishes a more accurate monitoring scheme for the location and scale of microseismic events generated by hydraulic fracturing of coal seam roof, enabling the effective capture of micro-fracture signal sources in the coal seam roof during hydraulic fracturing, improving the positioning accuracy of microseismic sources, and providing guidance and reference for hydraulic fracturing design. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the arrangement of the various groups of sensors provided in Embodiment 1 of the present invention;

[0026] Figure 2 for Figure 1 AA section view;

[0027] Figure 3 for Figure 1 BB section view;

[0028] in:

[0029] 1-Sensor I; 2-Sensor II; 3-Sensor III; 4-Sensor IV; 13-Hydraulic fracturing borehole I; 14-Hydraulic fracturing borehole II; 15-Hydraulic fracturing borehole III; 16-Belt conveyor roadway; 17-Auxiliary transport roadway. Detailed Implementation

[0030] To better explain and facilitate understanding of the present invention, the technical solution and effects of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] A method for arranging microseismic monitoring sensors suitable for hydraulic fracturing of coal seam roof, combined with... Figure 1-3 As shown, the details are as follows:

[0032] S1: Deploy the first set of sensors in the first connecting auxiliary transport roadway 17 and the belt transport roadway 16.

[0033] S1.1: On the roof of auxiliary transport roadway 17, drill long boreholes from one side of auxiliary transport roadway 17 toward belt transport roadway 16. All long boreholes are on one side of the hydraulic fracturing boreholes and form a certain angle with auxiliary transport roadway 17. Figure 2 As shown, the long borehole is located on one side of hydraulic fracturing boreholes I13, II 14, and III 15. Sensor I1 is arranged at the bottom of the long borehole. This sensor I1 is the first group of sensors I1 and is numbered 11. Sensor I1 is in a direction with an inclination angle of 75° perpendicular to the roadway advance direction, 63° to the working face advance direction, and 60° to the horizontal projection of the long borehole. The borehole length is 73.4m.

[0034] S1.2: Drill a short borehole perpendicular to the direction of the auxiliary transport roadway 17 on the rock wall between the auxiliary transport roadway 17 and the conveyor belt transport roadway 16. Place sensor Ⅲ3 at the bottom of the short borehole. This sensor Ⅲ3 is the first group of sensor Ⅲ3 and is numbered 13. The sensor Ⅲ3 is located directly above the conveyor belt transport roadway 16 towards the auxiliary transport roadway 17, perpendicular to the roadway advance direction at an angle of 38°. The borehole length is 4.5m.

[0035] S2: Along the working face advancing direction, deploy the second set of sensors in the next connecting roadway, namely the second connecting roadway auxiliary transport roadway 17 and the belt transport roadway 16.

[0036] S2.1: Drill a long borehole in the rock wall between the auxiliary transport roadway 17 and the conveyor belt transport roadway 16, perpendicular to the auxiliary transport roadway 17. The long borehole passes through the midpoint of the line connecting the centers of the two hydraulic fracturing boreholes below, namely hydraulic fracturing borehole II 14 and hydraulic fracturing borehole III 15. Arrange sensor II2 at the bottom of the long borehole. This sensor II2 is the first group of sensor II2 and is numbered 22. This sensor II2 is located directly above the conveyor belt transport roadway 16, perpendicular to the roadway advance direction at an angle of 54°, and the borehole length is 80.3m.

[0037] S2.2: Drill a short borehole perpendicular to the auxiliary transport roadway 17 on the rock wall between the auxiliary transport roadway 17 and the conveyor belt transport roadway 16. Arrange sensor No. 4, Ⅳ4, at the bottom of the short borehole. This sensor Ⅳ4 is the first group of sensor Ⅳ4 and is numbered 24. This sensor Ⅳ4 is located directly above the conveyor belt transport roadway 16 and is perpendicular to the roadway advance direction at an inclination angle of 45°. The borehole length is 4.5m.

[0038] In steps S1 and S2, the angles and directions of the long and short drill holes are different, and the four sensors are arranged in an alternating pattern on the vertical projection so that they can completely cover the area to be measured.

[0039] S3: As the tunnel advances, repeat steps S1 to S2, alternating between the first and second sets of sensors, as follows:

[0040] S3.1: The first set of sensors is installed in the borehole in the rock wall between the third connecting roadway auxiliary transport roadway 17 and the belt transport roadway 16.

[0041] S3.1.1: On the roof of the auxiliary transport roadway 17, a long borehole is drilled from one side of the auxiliary transport roadway 17 toward the belt transport roadway 16. The entire long borehole is on one side of the hydraulic fracturing borehole and forms a certain angle with the auxiliary transport roadway 17. A sensor I1 is arranged at the bottom of the long borehole. The sensor I1 is in a direction with an inclination angle of 75° perpendicular to the roadway advance direction, 63° with the working face advance direction, and 60° with the horizontal projection of the long borehole. The borehole length is 73.4m.

[0042] S3.1.2: Drill a short borehole perpendicular to the direction of the auxiliary transport roadway 17 on the rock wall between the auxiliary transport roadway 17 and the conveyor belt transport roadway 16, and place sensor Ⅲ3 at the bottom of the short borehole; the sensor Ⅲ3 is located directly above the conveyor belt transport roadway 16 towards the auxiliary transport roadway 17 at an angle of 38° perpendicular to the direction of roadway advancement, and the borehole length is 4.5m.

[0043] S3.2: Along the working face advance direction, the second set of sensors is arranged in the fourth connecting roadway auxiliary transport roadway 17 and the belt transport roadway 16.

[0044] S3.2.1: Drill a long borehole in the rock wall between the auxiliary transport roadway 17 and the conveyor belt transport roadway 16, perpendicular to the direction of the auxiliary transport roadway 17. The long borehole passes through the midpoint of the line connecting the centers of the two hydraulic fracturing boreholes below. Place sensor II2 at the bottom of the long borehole. Sensor II2 is located directly above the conveyor belt transport roadway 16, perpendicular to the direction of roadway advancement at an angle of 54°. The borehole length is 80.3m.

[0045] S3.2.2: Drill a short borehole perpendicular to the auxiliary transport roadway 17 on the rock wall between the auxiliary transport roadway 17 and the conveyor belt transport roadway 16, and place sensor No. 4, IV4, at the bottom of the short borehole; sensor IV4 is located directly above the conveyor belt transport roadway 16, perpendicular to the roadway advance direction at an inclination angle of 45°, and the borehole length is 4.5m.

[0046] In step S1, the sensor installed in the long borehole is 12m away from the center of the nearest hydraulic fracturing borehole. Both the long boreholes drilled with the first and second sets of sensors are at the same height as the hydraulic fracturing borehole furthest from the roadway. The short boreholes drilled with both sets of sensors are 26.5m away from the center of the nearest hydraulic fracturing borehole. All sensors used in this method are velocity-type sensors.

Claims

1. A method for arranging microseismic monitoring sensors suitable for hydraulic fracturing of coal seam roof, characterized in that, Specifically, the following steps are included: S1: The first set of sensors is arranged in the first connecting auxiliary transport roadway (17) and the belt transport roadway (16). S1.1: On the top plate of the auxiliary transport roadway (17), a long borehole is drilled from one side of the auxiliary transport roadway (17) toward the belt transport roadway (16). The entire long borehole is on one side of the hydraulic fracturing borehole and forms an angle with the auxiliary transport roadway (17); Sensor I (1) is arranged at the bottom of the long borehole. S1.2: Drill a short borehole perpendicular to the direction of the auxiliary transport roadway (17) on the rock wall between the auxiliary transport roadway (17) and the conveyor belt transport roadway (16), and place sensor Ⅲ (3) at the bottom of the short borehole. S2: Along the working face advance direction, deploy the second set of sensors in the next connecting auxiliary transport roadway (17) and belt transport roadway (16). S2.1: Drill a long borehole in the rock wall between the auxiliary transport roadway (17) and the conveyor belt transport roadway (16), perpendicular to the direction of the auxiliary transport roadway (17). The long borehole passes through the midpoint of the line connecting the centers of the two hydraulic fracturing boreholes below. Place sensor II (2) at the bottom of the long borehole. S2.2: Drill a short borehole perpendicular to the auxiliary transport roadway (17) on the rock wall between the auxiliary transport roadway (17) and the conveyor belt transport roadway (16), and place sensor Ⅳ (4) at the bottom of the short borehole. S3: As the tunnel advances, repeat steps S1~S2, alternating between the first and second sets of sensors; The angles and directions of the long and short drill holes in steps S1 and S2 are different, and the sensors arranged in the long and short drill holes are staggered in the vertical projection. In step S1, the sensor installed in the long borehole is 12m away from the center of the nearest hydraulic fracturing borehole. The long boreholes drilled when the first set of sensors is arranged and the long boreholes drilled when the second set of sensors is arranged are both at the same height as the hydraulic fracturing borehole farthest from the roadway. The short boreholes drilled when the first set of sensors is arranged and the short boreholes drilled when the second set of sensors is arranged are both 26.5m away from the center of the nearest hydraulic fracturing borehole.

2. The method for arranging microseismic monitoring sensors for hydraulic fracturing of coal seam roof according to claim 1, characterized in that: In step S1.1, sensor I (1) is in a direction with an inclination angle of 75° perpendicular to the roadway advance direction, at an angle of 63° to the working face advance direction, and at an angle of 60° to the horizontal projection of the long borehole, with a borehole length of 73.4m.

3. The method for arranging microseismic monitoring sensors suitable for hydraulic fracturing of coal seam roof according to claim 1, characterized in that: In step S1.2, sensor III (3) is located directly above the conveyor belt transport roadway (16) and the auxiliary transport roadway (17) at an angle of 38° perpendicular to the roadway advance direction, with a borehole length of 4.5m.

4. The method for arranging microseismic monitoring sensors suitable for hydraulic fracturing of coal seam roof according to claim 1, characterized in that: In step S2.1, sensor II (2) is located directly above the conveyor belt transport roadway (16) at an angle of 54° perpendicular to the roadway's advancing direction, with a borehole length of 80.3m.

5. The method for arranging microseismic monitoring sensors for hydraulic fracturing of coal seam roof according to claim 1, characterized in that: In step S2.2, sensor IV (4) is located directly above the conveyor belt transport roadway (16) at an angle of 45° perpendicular to the roadway's advancing direction, with a borehole length of 4.5m.

6. The method for arranging microseismic monitoring sensors for hydraulic fracturing of coal seam roof according to claim 1, characterized in that: The sensors used in this method are all velocity sensors.

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