Rock burst coal seam upper and lower region coordinated fracturing pre-control method

Abstract

The application provides a rock burst coal seam well upper and lower area coordinated fracturing pre-control method. First, the coal rock impact tendency is identified before the coal seam is mined, so as to judge the mine impact danger and demarcate the dangerous area, and the ground fracturing technology is used to fracture the roof of the dangerous area. In the mining process of the working face, the microseismic monitoring means is used to monitor the overburden rock breaking energy release strength in real time, and according to the monitoring result, the long borehole hydraulic fracturing technology is used to further pre-fracture and weaken the hard roof underground, so that the rock burst is prevented and controlled. The method is scientific and reliable, the technical means is comprehensive, the rock burst source can be weakened and controlled from the source, and the application prospect is wide.

Description

Technical Field

[0001] This invention relates to the field of rockburst disaster prevention and control technology in steeply inclined coal seam mining, and in particular to a method for coordinated fracturing pre-control of rockburst in the upper and lower regions of the coal seam. Background Technology

[0002] Rockbursts are a major hazard threatening safe coal mining, being the most difficult to control and causing the highest casualty rate. The frequency of rockbursts is also increasing annually. Scholars have conducted extensive research on the mechanisms of rockburst occurrence. Studies show that stress accumulation and energy release caused by geological dynamics and mining disturbances are the fundamental causes. Rockbursts mostly occur in mining areas with hard roofs because the roofs are strong and thick, making them difficult to break during mining, leading to energy accumulation and thus easily triggering rockbursts. However, current domestic and international efforts to control rockbursts have not yielded significant breakthroughs. Control measures are mostly limited to passive defense within the mine, failing to address the root causes. This results in persistent casualties and asset losses, severely impacting safe production in mines.

[0003] Therefore, scientific prediction and precise prevention of rockbursts are imperative. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a method for coordinated fracturing pre-control of coal seam areas above and below the well in the event of rockburst.

[0005] To achieve the above objectives, the present invention provides the following solution: A method for coordinated fracturing pre-control of coal seam above and below ground in the event of rockburst, comprising: Core samples were obtained by drilling holes in the working face and the top and bottom plates of the steeply inclined coal seam. The physical and mechanical parameters of the core samples were tested, and the impact tendency of the core samples was identified. The results were obtained, and the elevations a and b of the working face mining section of the steeply inclined coal seam and the dip angle α of the coal seam were marked. If the measurement result indicates no tendency to impact, then surface and underground fracturing is unnecessary. If the measurement result indicates a weak tendency to impact, then surface fracturing is unnecessary; only underground fracturing is performed using long boreholes to target the hard rock layer. The target hard rock layer is the thickest layer among the key rock layers within a 50m normal distance from the working face of the steeply inclined coal seam. The long boreholes are arranged on the centerline of the hard rock layer. The dip distance from the uppermost long borehole to the caving line is denoted as m, the vertical distance between the lowermost long borehole and the horizontal plane at elevation a is denoted as n, and the dip distance between two adjacent long boreholes is denoted as L. If the measurement result indicates a strong tendency to impact, then based on the working face of the steeply inclined coal seam and the tested physical and mechanical parameters of the roof and floor, a phase numerical simulation model is established at a 1:1 scale to simulate the stress concentration and energy accumulation characteristics of the overburden during the mining process of the steeply inclined coal seam. Energy accumulation in overburden ≥10 5 Mark the inclined rock strata of J and record the location of the inclined rock strata and the range of energy concentration areas; Deploy fracturing deviated wells on the surface to perform surface fracturing on the inclined rock strata within the marked range S; After surface fracturing, during the mining of steeply inclined coal seams, microseismic monitoring equipment is deployed underground for monitoring. If the energy of overburden fracturing is less than 10... 4 J, then no additional fracturing is required; if the energy of overlying rock fracture after fracturing is still monitored to be 10... 4 For depths above J, long boreholes are used for fracturing underground. The target layer for fracturing is the thickest layer of key rock strata within 50m of the working face of the steeply inclined coal seam. The long fracturing boreholes are arranged on the centerline of the hard rock strata.

[0006] Preferably, the physical and mechanical parameters include: tensile strength, compressive strength, Poisson's ratio, elastic modulus, deformation modulus, cohesion, and internal friction angle.

[0007] Preferably, the value of L is in the range of 40≤L≤50.

[0008] Preferably, the range of values ​​for m is: 10 ≤m≤25 .

[0009] Preferably, the value range of n is: 0.2L ≤n≤L .

[0010] Preferably, if the area S ≤ 400m, a surface fracturing shaft is arranged in the middle of the area S; if S > 400m, a surface fracturing shaft is arranged every 200m within the area S.

[0011] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: This invention provides a method for coordinated fracturing pre-control of coal seams in both underground and surface areas during rockburst, comprising: drilling core samples from the working face and the top and bottom plates of a steeply inclined coal seam; testing the physical and mechanical parameters of the core samples; identifying the rockburst tendency of the core samples; obtaining the measurement results; and marking the elevations a and b of the working face mining section and the dip angle α of the coal seam. If the measurement results indicate no rockburst tendency, no surface or underground fracturing is required. If the measurement results indicate a weak rockburst tendency, no surface fracturing is required; instead, long boreholes are used underground to fracture the target hard rock strata. The target hard rock strata are located in a steeply inclined coal seam. The thickest layer of key rock strata within a 50m normal distance from the working face of the inclined coal seam; long boreholes are arranged on the centerline of the hard rock strata, the dip distance of the uppermost long borehole from the caving line is denoted as m, the vertical distance between the lowermost long borehole and the horizontal plane at elevation a is denoted as n, and the dip distance between two adjacent long boreholes is denoted as L; if the measurement result indicates a strong impact tendency, then based on the working face of the steeply inclined coal seam and the tested physical and mechanical parameters of the roof and floor, a phase numerical simulation model is established at a 1:1 scale to simulate the stress concentration and energy accumulation characteristics of the overburden during the mining process of the steeply inclined coal seam; for overburden with accumulated energy ≥10 5 Mark the inclined rock strata of J, recording their location and the area of ​​energy concentration. Deploy a fracturing shaft on the surface to perform surface fracturing on the inclined rock strata within the marked area S. After surface fracturing, during the mining of the steeply inclined coal seam, deploy microseismic monitoring equipment underground for monitoring. If the energy of the fracturing overburden fracture is less than 10... 4 J, then no additional fracturing is required; if the energy of overlying rock fracture after fracturing is still monitored to be 10... 4 For rock bursts above J, long boreholes are used for fracturing underground. The target layer for fracturing is the thickest layer of key rock strata within 50m of the working face of the steeply inclined coal seam. The long fracturing boreholes are arranged along the centerline of the hard rock strata. This invention is scientifically reliable, with comprehensive technical means, and can weaken and control rockburst sources at their source, with broad application prospects. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 A flowchart of the method provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the technical route provided in the embodiments of the present invention; Figure 3A schematic diagram of the arrangement of a fracturing deviated well provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the plan layout of a fracturing deviated well provided in an embodiment of the present invention.

[0014] Explanation of reference numerals in the attached figures: 1-Working face, 2-Long borehole, 3-Hard rock strata, 4-Inclined rock strata, 5-Fracturing inclined well. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The purpose of this invention is to provide a method for coordinated fracturing and pre-control of coal seam rockburst in the upper and lower regions. This method is scientific, reliable, and comprehensive in its technical means. It can weaken and control the rockburst source from the source and has broad application prospects.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1 and Figure 2 As shown, this invention provides a method for coordinated fracturing pre-control of the upper and lower regions of a coal seam in the event of rockburst, comprising: Step 100: Drill core samples from the working face and the top and bottom plates of the steeply inclined coal seam to obtain core samples, test the physical and mechanical parameters of the core samples, identify the impact tendency of the core samples, obtain the measurement results, and mark the elevations a and b of the mining section of the steeply inclined coal seam working face and the dip angle α of the coal seam. Step 200: If the measurement result indicates no tendency to impact, then no surface or underground fracturing is required; if the measurement result indicates a weak tendency to impact, then no surface fracturing is required, and only underground fracturing is performed on the target hard rock layer using long boreholes; the target hard rock layer is the thickest layer of the key rock layer within a 50m normal distance from the working face of the steeply inclined coal seam; the long boreholes are arranged on the centerline of the hard rock layer, and the dip distance from the uppermost long borehole to the caving line is denoted as m, the vertical distance between the lowermost long borehole and the horizontal plane at elevation a is denoted as n, and the dip distance between two adjacent long boreholes is denoted as L; if the measurement result indicates a strong tendency to impact, then based on the working face of the steeply inclined coal seam and the tested physical and mechanical parameters of the roof and floor, a phase numerical simulation model is established at a 1:1 scale to simulate the stress concentration and energy accumulation characteristics of the overburden during the mining process of the steeply inclined coal seam. Step 300: Energy accumulation in overburden ≥10 5 Mark the inclined rock strata of J and record the location of the inclined rock strata and the range of energy concentration areas; Step 400: Deploy fracturing deviated wells on the surface to perform surface fracturing on the inclined rock strata within the marked range S; Step 500: After surface fracturing, during the mining of steeply inclined coal seams, microseismic monitoring equipment is deployed underground for monitoring. If the energy of overburden fracturing is less than 10... 4 J, then no additional fracturing is required; if the energy of overlying rock fracture after fracturing is still monitored to be 10... 4 For depths above J, long boreholes are used for fracturing underground. The target layer for fracturing is the thickest layer of key rock strata within 50m of the working face of the steeply inclined coal seam. The long fracturing boreholes are arranged on the centerline of the hard rock strata.

[0019] Specifically, such as Figure 3 and Figure 4 As shown, the main steps of this embodiment are as follows: a. Core samples were taken from boreholes in the steeply inclined coal seam working face 1 and its roof and floor plates to test its physical and mechanical parameters such as tensile strength, compressive strength, Poisson's ratio, elastic modulus, deformation modulus, cohesion, and internal friction angle. In accordance with national standards, its impact tendency was identified, and the elevations a and b of the mining section of the steeply inclined coal seam working face 1 and the coal seam dip angle α, α=60° were marked. b. If the test results indicate no tendency for impact, then surface and downhole fracturing is not required; c. If the measurement result indicates a weak impact tendency, then surface fracturing is unnecessary. Instead, long boreholes 2 are used underground to fracturing the target hard rock layer 3. The target hard rock layer 3 is the thickest layer among the key rock layers within a 50m normal distance from the steeply inclined coal seam working face 1. Long boreholes 2 are arranged on the centerline of the hard rock layer 3. The dip distance of the uppermost long borehole 2 from the caving line is denoted as m, the vertical distance between the lowermost long borehole 2 and the horizontal plane at elevation a is denoted as n, and the dip distance between two adjacent long boreholes 2 is denoted as L. c. If the judgment result is a strong impact tendency, then based on the physical and mechanical parameters of the steeply inclined coal seam working face 1 and the tested roof and floor, establish a corresponding numerical simulation model at a 1:1 scale to simulate the stress concentration and energy accumulation characteristics of the overburden during the mining of the steeply inclined coal seam working face 1. d. Energy accumulation in overburden ≥10 5 Mark the inclined rock layer 4 of J and record its location and the area S of energy concentration; e. Deploy fracturing deviated wells 5 on the surface to perform surface fracturing on the inclined rock strata 4 within the marked range S; f. After surface fracturing, during the mining of the steeply inclined coal seam working face 1, microseismic monitoring equipment should be installed underground for monitoring. If the energy of the overburden fracture after fracturing is less than 10... 4 J, then no additional fracturing is required; if the energy of overlying rock fracture after fracturing is still above 10... 4 If the fracturing is above J, then long borehole 2 will continue to be used for fracturing underground. The target layer for fracturing is the thickest layer of key rock strata within 50m of the normal distance of the steeply inclined coal seam working face 1. The arrangement of long borehole 2 for fracturing is the same as in step c.

[0020] Specifically, the parameter ranges in this embodiment are as follows: The range of L is 40 ≤ L ≤ 50, and the unit is meters. The range of values ​​for m is: 10 ≤m≤25 Unit: meters; The range of values ​​for n is: 0.2L ≤n≤L , Unit: meter.

[0021] Furthermore, if the area S ≤ 400m, a surface fracturing shaft 5 is arranged in the middle of the area S; if S > 400m, a surface fracturing shaft 5 is arranged every 200m within the area S.

[0022] Finally, we have: L = 40 meters; m = 25 tanα = 43 meters; n = 0.5Lsinα = 17 meters.

[0023] The energy concentration area of ​​this mine is S=300m, meaning that only one surface fracturing shaft 5 needs to be selected for rock fracturing.

[0024] The beneficial effects of this invention are as follows: 1) The parameters of the numerical calculation model are all taken from the field, which is real and reliable. The model is established at a 1:1 scale according to the geological conditions of the field mining, which ensures the accuracy of the prediction results. At the same time, the prediction model is easy to establish and has strong operability. 2) Ground fracturing technology is selectively applied based on prediction results, avoiding blind application of technology and unnecessary engineering work, and maximizing the advantages of each technology; 3) Using surface fracturing technology to control fracturing in the target layer is more operable, has a larger control range, and better fracturing effect compared with traditional downhole control technology. It truly achieves active control of rockburst from the source and has broad application prospects.

[0025] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0026] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for coordinated fracturing pre-control of coal seam areas above and below the well during rockburst, characterized in that, include: Core samples were obtained by drilling holes in the working face and the top and bottom plates of the steeply inclined coal seam. The physical and mechanical parameters of the core samples were tested, and the impact tendency of the core samples was identified. The results were obtained, and the elevations a and b of the working face mining section and the dip angle α of the coal seam were marked. If the measurement result indicates no tendency to impact, then surface and underground fracturing is unnecessary. If the measurement result indicates a weak tendency to impact, then surface fracturing is unnecessary; only underground fracturing is performed using long boreholes to target the hard rock layer. The target hard rock layer is the thickest layer among the key rock layers within a 50-meter normal distance from the working face of the steeply inclined coal seam. The long boreholes are arranged on the centerline of the hard rock layer. The dip distance from the uppermost long borehole to the caving line is denoted as m, the vertical distance between the lowermost long borehole and the horizontal plane at elevation a is denoted as n, and the dip distance between two adjacent long boreholes is denoted as L. If the measurement result indicates a strong tendency to impact, then based on the working face of the steeply inclined coal seam and the tested physical and mechanical parameters of the roof and floor, a phase numerical simulation model is established at a 1:1 scale to simulate the stress concentration and energy accumulation characteristics of the overburden during the mining process of the steeply inclined coal seam. Energy accumulation in overburden ≥10 5 Mark the inclined rock strata of J and record the location of the inclined rock strata and the range of energy concentration areas; Deploy fracturing inclined wells on the surface to perform surface fracturing on the inclined rock strata within the area S; After surface fracturing, during the mining of steeply inclined coal seams, microseismic monitoring equipment is deployed underground for monitoring. If the energy of overburden fracturing is less than 10... 4 J, then no additional fracturing is required; if the energy of overlying rock fracture after fracturing is still monitored to be 10... 4 If the fracturing depth is above J, long boreholes will continue to be used for fracturing underground. The target layer for fracturing is the thickest layer of key rock strata within 50m of the working face of the steeply inclined coal seam. The long fracturing boreholes are arranged on the center line of the hard rock strata. If the energy of overlying fracture after fracturing is still monitored to be above 10 4 If the fracturing is above J, then when long boreholes are used for fracturing in the well, the long boreholes are arranged in the manner of long boreholes under weak impact tendency, that is, the uppermost long fracturing borehole is m away from the collapse line, the lowermost long fracturing borehole is n vertically between the horizontal plane at elevation a, and the tendency distance between two adjacent long fracturing boreholes is L. The range of values ​​for m is: 10 ≤m≤25 The unit is meters; the range of n is 0.2L. ≤n≤L The unit is meters.

2. The method for coordinated fracturing pre-control of coal seam areas above and below the well site in case of rockburst, as described in claim 1, is characterized in that... The physical and mechanical parameters include: tensile strength, compressive strength, Poisson's ratio, elastic modulus, deformation modulus, cohesion, and internal friction angle.

3. The method for coordinated fracturing pre-control of coal seam areas above and below the well site in case of rockburst as described in claim 1, characterized in that, The range of L is 40≤L≤50, and the unit is meters.

4. The method for coordinated fracturing pre-control of coal seam above and below ground in the event of rockburst according to claim 1, characterized in that, If the area S ≤ 400 meters, a surface fracturing shaft is arranged in the middle of the area S; if S > 400 meters, a surface fracturing shaft is arranged every 200 meters within the area S.

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