Method for controlling rock burst through hydraulic fracturing of coal seam roof

Abstract

The invention discloses a method for treating rock burst through coal seam roof hydraulic fracturing, and belongs to the technical field of coal mining. The method comprises the steps that a high-pressure pump station is built on the ground, a directional inclined shaft is constructed in the high-pressure pump station, and a high-pressure pipeline is conveyed to a shaft station; determining an overlying strata key layer by using a key layer theory, and calculating fracturing radiuses under different pressure and flow parameters; drilling holes in the key layer by using an underground drill rig; the fracturing tool string is sent into the drill hole of the key layer; a ground fracturing fluid conveying pipeline is connected with the in-hole fracturing tool string through a high-pressure pipeline; operating a fracturing pump truck group to inject high-pressure fluid into the drill hole for fracturing to generate cracks; a micro-seismic fracture monitoring system is used for monitoring the development condition of the fracturing fracture; the distance between fracturing sections is adjusted by means of the monitored expansion range of the fracturing fractures, and it is guaranteed that the fracturing fractures in the key layer are communicated with one another; the ground high-pressure pump station and the underground fracturing tool string are connected to form a set of well-ground combined fracturing system, the fracturing effect can be improved after the fracturing system is started, the whole construction period is shortened, and the cost is low.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, and in particular to a method for controlling rock burst by hydraulic fracturing of a coal seam roof. Background Art

[0002] At present, hydraulic fracturing for rock burst control is mainly divided into two aspects: surface fracturing and downhole fracturing. Surface fracturing has large scale, high displacement, large extension of fractures and excellent control effect, but surface fracturing occupies a large area (4000m 2 ), land acquisition coordination and well site repair are difficult, and the construction period is often too long to meet the needs of underground production; underground hydraulic fracturing is limited by the site, the displacement of the fracturing pump is too small, and the underground water supply is difficult, the extension of the hydraulic fracture is not ideal, and the treatment effect is poor. Summary of the invention

[0003] In order to solve the problems of the prior art, the present invention provides a method for controlling rock burst by hydraulic fracturing of a coal seam roof, comprising:

[0004] Step 1: Establish a high-pressure pump station, construct a directional inclined well in the high-pressure pump station, and deliver the high-pressure pipe to the well bottom parking lot;

[0005] Step 2, determine the key layers of the overburden;

[0006] Step 3, calculating the fracturing radius when drilling holes in the key layer;

[0007] Step 4, drilling holes in the key layer, with the drilling spacing covering the entire working surface with the fracturing radius;

[0008] Step 5, inserting the fracturing tool string into the borehole of the key layer;

[0009] Step 6, using a high-pressure pipe to connect the surface fracturing fluid pipeline to the in-hole fracturing tool in series;

[0010] Step 7, the ground-operated fracturing pump truck injects high-pressure fluid into the borehole for fracturing to generate cracks;

[0011] Step 8, monitoring the development of hydraulic fractures through a ground microseismic fracture monitoring system;

[0012] Step 9, using the monitored expansion range of the hydraulic fractures, adjust the spacing of the hydraulic fracture sections to ensure that the hydraulic fractures in the key layers are interconnected.

[0013] Furthermore, in step 1, the overburden key layer is determined based on the mine geological comprehensive column chart, the location of the microseismic event source, three-zone observations of adjacent mining working faces and the key layer theory.

[0014] Furthermore, in step 3, the fracturing radius is calculated based on the displacement of the ground fracturing pump truck group and the lithology, thickness and compressive strength parameters of the key layer.

[0015] Furthermore, in step 4, directional drilling is performed on the key layer in the return air chute or retreat channel of the underground working face using an underground tunnel drilling rig.

[0016] Furthermore, in step 5, a downhole tunnel drill is used to send the fracturing tool string into the borehole on the key layer.

[0017] Furthermore, in step 7, warning signs and cameras are set in the underground tunnels, and the cameras monitor the borehole mouth response at all times and send the acquired data to the background control center.

[0018] Further, in step 8, the microseismic crack monitoring system includes: a detection instrument and a GPS;

[0019] The monitoring instrument is arranged near the working face, and the detector substations are arranged within the fracturing setting range. The monitored area is surrounded by lines in the order of the substations. The distance between adjacent substations is greater than 100 meters. The GPS is used to measure the wellhead of the horizontal well and the coordinates of each substation to monitor the orientation, length, depth and spacing of the fractures.

[0020] Beneficial effects of the present invention:

[0021] By establishing a high-pressure pump station in the mining area, a roof hole is constructed in the predetermined layer by using a directional drill in the return air chute of the underground working face, and a fracturing tool string is sent into the hole. Then, a connecting hole is constructed from the ground high-pressure pump station area to the underground main tunnel, and then the ground high-pressure pump station and the underground fracturing tool string are connected to form a well-ground combined fracturing system. After the fracturing system is started, the fracturing effect can be improved, the entire construction period is shortened, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 It is a schematic diagram of the rock burst control process provided by the present invention;

[0024] Figure 2 It is a schematic diagram of the construction of a high-pressure pump station provided by the present invention;

[0025] Figure 3It is a schematic diagram of key layer construction provided by the present invention. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0027] See also Figure 1-3 A method for controlling rock burst by hydraulic fracturing of a coal seam roof, comprising:

[0028] Step 1: Establish a high-pressure pump station, construct a directional inclined well in the high-pressure pump station, and deliver the high-pressure pipe to the well bottom parking lot;

[0029] A permanent high-pressure pump station is established at a reasonable location in the industrial square, equipped with fracturing pump trucks, sand mixing trucks, water storage tanks and other equipment required for fracturing, and a directional inclined well is constructed in the pump station to transport the high-pressure manifold to the bottom of the well.

[0030] Step 2, determine the overburden key layer based on the mine geological comprehensive column chart, the location of the microseismic event source, the three-zone observation of the adjacent mining working face and the key layer theory;

[0031] When the overburden ruptures suddenly, a large-energy microseismic event will occur, that is, elastic waves are transmitted in the rock mass. By arranging multiple sets of sensors in the area above the coal seam and collecting effective data in real time, after processing by data processing software, the location of the rupture can be determined by positioning software and displayed in three-dimensional space; then, the dynamic evolution characteristics and laws of the mining rock cracks are analyzed through the determined three-dimensional spatial positioning map, and the topological network structure of the microseismic monitoring system is established to accurately determine the location of the key layer.

[0032] In addition, based on the geological conditions of the coal seam roof and the historical data of rock burst, the target roof layer that needs hydraulic fracturing and its specific location are determined.

[0033] Step 3, calculating the fracturing radius according to the displacement of the ground fracturing pump truck group and parameters such as the lithology, thickness, and compressive strength of the key layer.

[0034] Step 4: Directional drilling is performed on the key layer in the return air chute or retreat channel of the underground working face using an underground tunnel drilling rig, and the drilling spacing is set until the entire working face is covered by the fracturing radius.

[0035] Step 5: Use an underground tunnel drill to deliver the fracturing tool string to the designated position in the hole (with reasonable spacing to ensure that the fractures can communicate with each other).

[0036] Step 6: Use a high-pressure manifold to connect the surface fracturing fluid pipeline to the in-hole fracturing tool string.

[0037] Step 7: The ground-operated fracturing pump truck injects high-pressure water to perform fracturing to generate fissures; personnel are sent to raise the alert in the underground tunnel, and cameras are used to monitor the orifice response at all times.

[0038] Among them, high-pressure water flow and fracturing fluid are injected into long drill holes and branch holes. The pressure of the water flow causes cracks in the roof and expands. During the fracturing process, parameters such as injection pressure, flow rate and fracturing fluid ratio must be strictly controlled to ensure the fracturing effect and avoid adverse effects on the surrounding environment.

[0039] In order to increase the fracturing effect, detailed geological exploration and formation analysis are carried out before the fracturing operation to understand the lithology, porosity, permeability and other parameters of the target formation.

[0040] According to the results of geological analysis, a reasonable injection volume of fracturing fluid is designed to ensure that the cracks can be effectively opened without causing waste of resources.

[0041] Step 8: Use a ground microseismic crack monitoring system to monitor the development of hydraulic fractures. Arrange the monitoring instrument near the working face, deploy substations within the hydraulic setting range, and connect the substations in sequence to surround the monitored area. The spacing between adjacent substations is greater than 100 meters. Use high-precision GPS to measure the wellhead of the horizontal well and the coordinates of each substation to monitor the orientation, length, depth, and spacing of the fractures.

[0042] Step 9, using the monitored fracture expansion radius, adjust the spacing of the fracture sections to ensure that the fractures in the key layer are interconnected.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling rock burst by hydraulic fracturing of coal seam roof, characterized in that: include: Step 1: Establish a high-pressure pump station, construct a directional inclined well in the high-pressure pump station, and deliver the high-pressure pipe to the well bottom parking lot; Step 2, determine the key layers of the overburden; Step 3, calculating the fracturing radius when drilling holes in the key layer; Step 4, drilling holes in the key layer, with the drilling spacing covering the entire working surface with the fracturing radius; Step 5, inserting the fracturing tool string into the borehole of the key layer; Step 6, using a high-pressure pipe to connect the surface fracturing fluid pipeline to the in-hole fracturing tool in series; Step 7, the ground-operated fracturing pump truck injects high-pressure fluid into the borehole for fracturing to generate cracks; Step 8, monitoring the development of hydraulic fractures through a ground microseismic fracture monitoring system; Step 9, using the monitored expansion range of the hydraulic fractures, adjust the spacing of the hydraulic fracture sections to ensure that the hydraulic fractures in the key layers are interconnected.

2. The method for controlling rock burst by hydraulic fracturing of coal seam roof according to claim 1, characterized in that: In step 1, the overburden key layer is determined based on the mine geological comprehensive column chart, the location of the microseismic event source, the three-zone observation of the adjacent mining working face and the key layer theory.

3. The method for controlling rock burst by hydraulic fracturing of coal seam roof according to claim 1, characterized in that: In step 3, the fracturing radius is calculated according to the displacement of the ground fracturing pump truck group and the lithology, thickness and compressive strength parameters of the key layer.

4. The method for controlling rock burst by hydraulic fracturing of coal seam roof according to claim 1, characterized in that: In step 4, directional drilling is performed on the key layer in the return air chute or the withdrawal channel of the underground working face using an underground tunnel drilling rig.

5. The method for controlling rock burst by hydraulic fracturing of coal seam roof according to claim 1, characterized in that: In step 5, a downhole tunnel drill is used to send a fracturing tool string into a borehole on the key layer.

6. The method for controlling rock burst by hydraulic fracturing of coal seam roof according to claim 1, characterized in that: In step 7, warning signs and cameras are set up in the underground tunnel. The camera monitors the borehole mouth response at all times and sends the acquired data to the background control center.

7. The method for controlling rock burst by hydraulic fracturing of coal seam roof according to claim 1, characterized in that: In step 8, the microseismic crack monitoring system includes: a detection instrument and a GPS; The monitoring instrument is arranged near the working face, and the detector substations are arranged within the fracturing setting range. The monitored area is surrounded by lines in the order of the substations. The distance between adjacent substations is greater than 100 meters. The GPS is used to measure the wellhead of the horizontal well and the coordinates of each substation to monitor the orientation, length, depth and spacing of the fractures.

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