Microseismic monitoring sensor arrangement method suitable for hydraulic fracturing of coal seam roof

Abstract

The invention relates to a micro-seismic monitoring sensor arrangement method suitable for hydraulic fracturing of a coal seam roof, and belongs to the technical field of coal mining. The micro-seismic monitoring sensor arrangement method specifically comprises the following steps: S1, drilling a long hole in a roof of an auxiliary haulage roadway from one side of the auxiliary haulage roadway to a rubber belt haulage roadway, short drill holes are drilled in the rock wall between the auxiliary haulage roadway and the rubber belt haulage roadway in the direction perpendicular to the auxiliary haulage roadway, and sensors are arranged at the bottoms of the holes; s2, drilling long drill holes in the rock wall between the auxiliary haulage roadway and the rubber belt haulage roadway in the next linked roadway, drilling short drill holes perpendicular to the auxiliary haulage roadway in the rock wall between the auxiliary haulage roadway and the rubber belt haulage roadway in the direction perpendicular to the advancing direction of the working face, and arranging sensors at the bottoms of the holes; and S3, advancing along with the roadway, and repeating the steps S1 to S2. According to the invention, effective capture of a roof micro-fracture signal source in hydraulic fracturing of a coal seam is realized, and the positioning precision of a micro-seismic source is improved.

Description

Technical Field

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

[0002] As coal resources are mined deeper, deep mine pressure has gradually become one of the main disasters affecting mine safety production. When mining is carried out in underground coal seams, the overlying rock strata of the coal seams continue to fall, bend, slide, break, and other activities as the coal mining face advances, causing continuous changes in energy and stress in the mining area. These changes are ultimately manifested in the stress of the working face support, deformation of the surrounding rock, and failure of the support body, which can easily lead to dynamic disasters in the mine. In order to pre-control and prevent such risks and hidden dangers, it is necessary to pre-treat the thick and hard roof of the tunnel. In the process of coal mining, directional long-hole hydraulic fracturing is often used to destroy the integrity of the roof, reduce the stress concentration strength, and reduce the risk of sudden collapse of the hard roof causing disasters. Since traditional technical means are difficult to intuitively detect subtle pressure changes, there are relatively few studies on the laws of roof activity under hydraulic fracturing. Compared with traditional physical observation methods, microseismic monitoring technology can more accurately observe the subtle changes in roof activity after hydraulic fracturing. Research on roof activity patterns under microseismic directional long-hole hydraulic fracturing is of great significance for safe and efficient mining of coal mines.

[0003] As a three-dimensional regional vibration wave monitoring method, microseismic monitoring technology uses the acoustic emission phenomenon caused by rock crushing after hydraulic fracturing in the monitored area, and captures the microseismic signals generated during the fracture by deploying sensors. 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. It can provide accurate information on the location and scale of hydraulic fracturing activities through monitoring and analysis of tiny vibration signals, providing strong support for the safe management of roof pressure in coal mining and the feasibility study of releasing stress concentration in the roof of coal seams through hydraulic fracturing.

[0004] A Chinese patent (publication number: CN118191967A, publication date: June 14, 2024) discloses a full-space three-dimensional monitoring intelligent early warning system and method for coal seam roof water hazard risk, including a hydrological monitoring subsystem, a microseismic monitoring subsystem, a continuous electrical monitoring subsystem, a database server, a data processing center, and a roof water hazard monitoring and early warning platform; on the basis of the static evaluation of coal seam roof water hazard risk, the data interpretation and processing results of hydrological monitoring, microseismic monitoring and continuous electrical monitoring are integrated to carry out coal seam roof water hazard early warning. The invention integrates the hydrological monitoring subsystem, the microseismic monitoring subsystem, the continuous electrical monitoring subsystem, the water hazard risk assessment subsystem and the water hazard early warning subsystem, and the monitoring data is more comprehensive. The IHHO-Att-LSTM water hazard risk level intelligent early warning model is constructed, which can provide real-time intelligent early warning of coal seam roof water hazard risk with higher early warning accuracy. However, the technical difficulty in implementing directional long boreholes during roof monitoring is relatively high, and the position and direction of the borehole cannot be accurately located, resulting in inaccurate distance measurement.

[0005] Due to the limitation of sensor layout in the tunnel direction, the installation height and installation position cannot refer to the traditional layout method. Conventional underground roof monitoring usually arranges microseismic sensors at a certain distance above the tunnel wall or above the tunnel wall. Since the hydraulic fracturing signal is relatively weak and the propagation distance is relatively short, and for the drilling site where the highest borehole is arranged at a high distance from the tunnel surface, the conventional layout method has poor accuracy and does not meet the monitoring requirements. Therefore, hydraulic fracturing roof monitoring cannot use the conventional sensor layout method, and a new sensor layout method is required. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a method for arranging microseismic monitoring sensors suitable for hydraulic fracturing of coal seam roof.

[0007] A method for arranging microseismic monitoring sensors for hydraulic fracturing of coal seam roof specifically comprises the following steps:

[0008] S1: Arrange the first set of sensors in the first auxiliary transport lane (17) and the belt transport lane (16)

[0009] S1.1: On the roof of the auxiliary transport tunnel (17), a long borehole is drilled from one side of the auxiliary transport tunnel (17) toward the belt transport tunnel (16), wherein the long borehole is located on one side of the hydraulic fracturing borehole and forms an angle with the auxiliary transport tunnel (17); a sensor I (1) is arranged at the bottom of the long borehole;

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

[0011] S2: Arrange the second set of sensors in the next joint auxiliary transport lane (17) and belt transport lane (16) along the working face advancement direction.

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

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

[0014] S3: As the tunnel advances, steps S1 to S2 are repeated, and the first and second groups of sensors are arranged alternately.

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

[0016] In the step S1.2, the sensor III (3) is located directly above the belt transport lane (16) toward the auxiliary transport lane (17) at an angle of 38° perpendicular to the lane advancement direction, and the drilling length is 4.5 m.

[0017] In step S2.1, sensor II (2) is located directly above the belt conveyor tunnel (16) at an angle of 54° perpendicular to the tunnel advancement direction, and the drilling length is 80.3 m.

[0018] In step S2.2, sensor IV (4) is located directly above the belt conveyor tunnel (16) at an angle of 45° perpendicular to the tunnel advancement direction, and the drilling length is 4.5 m.

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

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

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

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

[0023] The present invention provides a method for arranging microseismic monitoring sensors suitable for hydraulic fracturing of coal seam roofs. Sensors are arranged in auxiliary transport lanes and belt transport lanes on the roof of the auxiliary transport lanes. In each group of sensor arrangements, long boreholes and short boreholes are drilled. The long and short envelope hole arrangement method is more conducive to increasing the accuracy of measurement. The sensors arranged in the long boreholes and the sensors arranged in the short boreholes can simultaneously measure the microseismic events generated by hydraulic fracturing at different depths. By comparing the measurement results of the sensors arranged in the long boreholes and the sensors arranged in the short boreholes, the location and size of the microseismic events can be observed more accurately and comprehensively, while improving the accuracy of the measurement, the accuracy of the measurement results can be mutually verified, and the probability of measurement errors caused by the failure of a single sensor can be reduced. In addition, measurements of multiple positions can be performed simultaneously, thereby improving the efficiency of the measurement. This can save time and labor costs for projects such as envelope drilling that require a large number of measurement points.

[0024] The present invention establishes a monitoring scheme for more accurately monitoring the location and scale of microseismic events caused by hydraulic fracturing of the coal seam roof, thereby effectively capturing the signal source of micro-fractures in the coal seam roof during hydraulic fracturing, improving the positioning accuracy of the microseismic source, and providing guidance and reference for hydraulic fracturing design. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the arrangement of each group of sensors provided in Example 1 of the present invention;

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

[0027] Figure 3 for Figure 1 BB cross-sectional 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 transport lane; 17-Auxiliary transport lane. DETAILED DESCRIPTION

[0030] In order to better explain the present invention and facilitate understanding, the technical solutions and effects of the present invention are described in detail below through specific implementation modes in conjunction with the accompanying drawings.

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

[0032] S1: Arrange the first set of sensors in the first joint auxiliary transport lane 17 and the belt transport lane 16

[0033] S1.1: On the roof of the auxiliary transport tunnel 17, a long borehole is drilled from one side of the auxiliary transport tunnel 17 to the direction of the belt transport tunnel 16. The long boreholes are all on one side of the hydraulic fracturing borehole and form a certain angle with the auxiliary transport tunnel 17, such as Figure 2 As shown, the long borehole is located as a whole on one side of hydraulic fracturing borehole I13, hydraulic fracturing borehole II 14, and hydraulic fracturing borehole III 15; a sensor I1 is arranged at the bottom of the long borehole, and the sensor I1 is the sensor I1 of the first group, numbered 11; the sensor I1 is oriented at an angle of 75° perpendicular to the advancement direction of the tunnel, 63° to the advancement direction of the working face, and 60° to the horizontal projection of the long borehole, and the borehole length is 73.4m.

[0034] S1.2: Drill a short hole on the rock wall between the auxiliary transport tunnel 17 and the belt transport tunnel 16, perpendicular to the direction of the auxiliary transport tunnel 17, and arrange sensor III3 at the bottom of the short hole. The sensor III3 is the first group of sensor III3 and is numbered 13. The sensor III3 is located directly above the belt transport tunnel 16 toward the auxiliary transport tunnel 17, perpendicular to the tunnel advancement direction, with an inclination of 38°, and the length of the hole is 4.5m.

[0035] S2: Arrange the second set of sensors in the next joint lane, the second joint lane auxiliary transport lane 17 and the belt transport lane 16, along the working face advancement direction.

[0036] S2.1: Drill a long borehole on the rock wall between the auxiliary transport tunnel 17 and the belt transport tunnel 16, perpendicular to the direction of the auxiliary transport tunnel 17. The long borehole passes through the midpoint of the center line of the two hydraulic fracturing boreholes below, namely, hydraulic fracturing borehole II 14 and hydraulic fracturing borehole III 15. A sensor Ⅱ2 is arranged at the bottom of the long borehole. The sensor Ⅱ2 is the sensor Ⅱ2 of the first group and is numbered 22. The sensor Ⅱ2 is located directly above the belt transport tunnel 16 and is perpendicular to the tunnel advancement direction with an inclination angle of 54°. The length of the borehole is 80.3m.

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

[0038] The long holes and short holes in steps S1 and S2 have different angles and directions, and the four sensors are arranged in a staggered manner in the vertical projection so as to completely cover the area to be measured.

[0039] S3: As the tunnel advances, repeat steps S1 to S2, alternately arranging the first and second groups of sensors, as follows:

[0040] S3.1: Arrange the first set of sensors in the rock wall borehole between the third joint auxiliary transport tunnel 17 and the belt transport tunnel 16:

[0041] S3.1.1: On the roof of the auxiliary transport tunnel 17, a long borehole is drilled from one side of the auxiliary transport tunnel 17 to the direction of the belt transport tunnel 16. The long boreholes are all on one side of the hydraulic fracturing borehole and form a certain angle with the auxiliary transport tunnel 17. A sensor I1 is arranged at the bottom of the long borehole; the sensor I1 is inclined at a direction perpendicular to the tunnel advancement direction with an angle of 75°, 63° to the working face advancement direction, and 60° to the horizontal projection of the long borehole. The borehole length is 73.4m.

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

[0043] S3.2: Arrange the second set of sensors in the fourth joint auxiliary transport lane 17 and the belt transport lane 16 along the working face advancement direction

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

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

[0046] The sensor set in the long borehole in step S1 is 12m away from the center of the nearest hydraulic fracturing borehole, and the long boreholes drilled when the first group of sensors are arranged and the long boreholes drilled when the second group of sensors are arranged are at the same height as the hydraulic fracturing borehole farthest from the roadway, and the short boreholes drilled when the first group of sensors are arranged and the short boreholes drilled when the second group of sensors are arranged are 26.5m away from the center of the nearest hydraulic fracturing borehole. The sensors used in this method are all velocity sensors.

Claims

1. A method for arranging microseismic monitoring sensors for hydraulic fracturing of coal seam roof, characterized in that: The specific steps include: S1: Arrange the first set of sensors in the first auxiliary transport lane (17) and the belt transport lane (16) S1.1: On the roof of the auxiliary transport tunnel (17), a long borehole is drilled from one side of the auxiliary transport tunnel (17) toward the belt transport tunnel (16), wherein the long borehole is located on one side of the hydraulic fracturing borehole and forms an angle with the auxiliary transport tunnel (17); a sensor I (1) is arranged at the bottom of the long borehole; S1.2: Drill a short borehole on the rock wall between the auxiliary transport tunnel (17) and the belt transport tunnel (16) perpendicular to the direction of the auxiliary transport tunnel (17), and arrange sensor III (3) at the bottom of the short borehole; S2: Arrange the second set of sensors in the next joint auxiliary transport lane (17) and belt transport lane (16) along the working face advancement direction. S2.1: Drill a long borehole on the rock wall between the auxiliary transport tunnel (17) and the belt transport tunnel (16), perpendicular to the direction of the auxiliary transport tunnel (17), the long borehole passes through the midpoint of the line connecting the centers of the two hydraulic fracturing boreholes below, and arrange sensor II (2) at the bottom of the long borehole; S2.2: Drill a short borehole perpendicular to the auxiliary transport tunnel (17) on the rock wall between the auxiliary transport tunnel (17) and the belt transport tunnel (16), and arrange sensor IV (4) at the bottom of the short borehole; S3: As the tunnel advances, steps S1 to S2 are repeated, and the first and second groups of sensors are arranged alternately.

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

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

4. The method for arranging microseismic monitoring sensors for coal seam roof hydraulic fracturing according to claim 1 is characterized in that: In step S2.1, sensor II (2) is located directly above the belt conveyor tunnel (16) at an angle of 54° perpendicular to the tunnel advancement direction, and the drilling length is 80.3 m.

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

6. The method for arranging microseismic monitoring sensors for coal seam roof hydraulic fracturing according to claim 1 is characterized in that: The long boreholes and short boreholes in steps S1 and S2 have different angles and directions, and the sensors arranged in the long boreholes and short boreholes are arranged in a staggered manner in vertical projection.

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

8. The method for arranging microseismic monitoring sensors for coal seam roof hydraulic fracturing according to claim 1 is characterized in that: The sensor arranged in the long borehole in step S1 is 12 m away from the center of the nearest hydraulic fracturing borehole, and the long borehole drilled when the first group of sensors are arranged and the long borehole drilled when the second group of sensors are arranged are at the same height as the hydraulic fracturing borehole farthest from the tunnel, and the short borehole drilled when the first group of sensors are arranged and the short borehole drilled when the second group of sensors are arranged are both 26.5 m away from the center of the nearest hydraulic fracturing borehole.

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