1. A method for preventing rock burst by hydraulic fracturing of an upper coal mine and a lower coal mine is characterized by comprising the following steps:

step 1, determining a key layer of overlying rock of a coal face, a fracturing layer of a horizontal well on the ground and a hydraulic fracturing layer of a top plate under the coal face;

step 2, constructing an L-shaped horizontal well on the ground to perform staged fracturing on a fracturing layer of the ground horizontal well;

and 3, performing hydraulic fracturing on the underground top plate hydraulic fracturing layer by the advanced coal face before stoping of the coal face, so that all rock strata below the rock-covering key layer of the coal face regularly collapse.

2. The method for preventing and treating rock burst through hydraulic fracturing on an underground coal mine according to claim 1, wherein in the step 1, a key rock covering layer and a direct caving layer of the coal face are determined according to a mine geological comprehensive histogram, a microseismic event seismic source position, three-zone observation of an adjacent stope face and a key layer theory, a rock stratum between the key rock covering layer and the direct caving layer of the coal face is determined to be a ground horizontal well fracturing layer, and the direct caving layer is determined to be a top plate hydraulic fracturing layer in the mine.

3. The method for preventing rock burst in coal mine underground hydraulic fracturing as claimed in claim 1, wherein said step 2 comprises the following steps:

step 2.1, constructing a vertical shaft section, and sleeving to reinforce a well mouth after completion;

2.2, constructing the vertical shaft to a position 30-100 m above a fracturing layer of the horizontal well on the ground, and starting deflecting;

2.3, adopting a directional system to horizontally drill in a fracturing layer of the horizontal well on the ground, and withdrawing the drill rod after drilling to a specified position;

and 2.4, starting hydraulic fracturing on the horizontal section until all the horizontal sections of the fracturing layer of the ground horizontal well are fractured.

4. The method for preventing rock burst in coal mine underground hydraulic fracturing as claimed in claim 3, wherein said step 2.4 is specifically: and (3) lowering the packer or the bridge plug, injecting high-pressure water into the two-stage packer or the bridge plug for fracturing, wherein the fracturing is integrally carried out in a retreating mode, and injecting a fracture proppant continuously in the fracturing process.

5. The method for preventing and treating rock burst by hydraulic fracturing on an underground coal mine according to claim 4, wherein the fracture proppant is fracturing fluid and fine sand.

6. The method for preventing rock burst in coal mine underground hydraulic fracturing as claimed in claim 1, wherein said step 3 comprises the following steps:

3.1, drilling holes at the hydraulic fracturing layer position of the underground roof from the part above the waist line of the roadway coal wall of the advanced coal face of 300m, wherein the inclination angle is 20-50 degrees;

step 3.2, fracturing from the bottom of the drill hole to the hole opening step by step, wherein the fracturing interval is 5m, and according to the number of microseismic events and the position of a seismic source, the parameters of the depth, the water pressure and the angle of the hydraulic fracturing hole of the underground top plate are modified and adjusted to maintain the stable pressure of the fracturing curve;

and 3.3, determining the distance between the underground hydraulic fracturing drilling holes as the periodic pressure step distance of the working face, and repeating the steps 3.1-3.2 until the coal face is fractured to a coal mining stopping line.

Background

Rock burst is one of the main disasters faced in coal mining of deep mines, and immeasurable loss is caused to mines and personnel. According to statistics, the impact mine pressure accidents mostly occur in roadways, more than half of the accidents occur in two advancing roadways of a working face, in the actual production process, the impact disasters mostly take roof plate types as main reasons, and particularly for hard roof mining areas in China, due to the fact that the roof plate is high in strength and large in thickness, the roof plate is not easy to break in the mining process, energy accumulation is caused, and rock burst is easy to induce. However, the traditional top plate blasting pre-splitting in China is influenced by factors such as underground roadways and charging modes, the hard top plate above the coal seam top plate by more than 50m is difficult to perform effective pre-splitting, and blasting is performed in the underground roadways, so that certain risks are caused. Therefore, how to safely and efficiently pre-crack the hard roof above the coal seam becomes a key factor for solving the rock burst of the coal face.

Disclosure of Invention

The invention aims to provide a method for preventing rock burst by hydraulic fracturing of an upper part and a lower part of a coal mine, which can realize the advance and three-dimensional weakening of a hard top plate of a rock burst mine and control a rock burst disaster from the source.

The technical scheme adopted by the invention is as follows: a method for preventing rock burst by hydraulic fracturing of an upper coal mine and a lower coal mine comprises the following steps:

step 1, determining a key layer of overlying rock of a coal face, a fracturing layer of a horizontal well on the ground and a hydraulic fracturing layer of a top plate under the coal face;

step 2, constructing an L-shaped horizontal well on the ground to perform staged fracturing on a fracturing layer of the ground horizontal well;

and 3, performing hydraulic fracturing on the underground top plate hydraulic fracturing layer by the advanced coal face before stoping of the coal face, so that all rock strata below the rock-covering key layer of the coal face regularly collapse.

The present invention is also characterized in that,

in the step 1, determining a coal face overlying rock key layer and a direct caving layer according to a mine geological comprehensive histogram, a microseismic event seismic source position, three-zone observation of adjacent stope faces and a key layer theory, further determining that a rock stratum between the coal face overlying rock key layer and the direct caving layer is a ground horizontal well fracturing layer, and determining that the direct caving layer is a downhole roof hydraulic fracturing layer.

The step 2 specifically comprises the following steps:

step 2.1, constructing a vertical shaft section, and sleeving to reinforce a well mouth after completion;

2.2, constructing the vertical shaft to a position 30-100 m above a fracturing layer of the horizontal well on the ground, and starting deflecting;

2.3, adopting a directional system to horizontally drill in a fracturing layer of the horizontal well on the ground, and withdrawing the drill rod after drilling to a specified position;

and 2.4, starting hydraulic fracturing on the horizontal section until all the horizontal sections of the fracturing layer of the ground horizontal well are fractured.

The step 2.4 is specifically as follows: and (3) lowering the packer or the bridge plug, injecting high-pressure water into the two-stage packer or the bridge plug for fracturing, wherein the fracturing is integrally carried out in a retreating mode, and injecting a fracture proppant continuously in the fracturing process.

The fracture proppant is fracturing fluid and fine sand.

The step 3 specifically comprises the following steps:

3.1, drilling holes at the hydraulic fracturing layer position of the underground roof from the part above the waist line of the roadway coal wall of the advanced coal face of 300m, wherein the inclination angle is 20-50 degrees;

step 3.2, fracturing from the bottom of the drill hole to the hole opening step by step, wherein the fracturing interval is 5m, and according to the number of microseismic events and the position of a seismic source, the parameters of the depth, the water pressure and the angle of the hydraulic fracturing hole of the underground top plate are modified and adjusted to maintain the stable pressure of the fracturing curve;

and 3.3, determining the distance between the underground hydraulic fracturing drilling holes as the periodic pressure step distance of the working face, and repeating the steps 3.1-3.2 until the coal face is fractured to a coal mining stopping line.

The invention has the beneficial effects that: the invention relates to a method for preventing and treating rock burst by hydraulic fracturing of an upper part and a lower part of a coal mine, which comprises the steps of performing staged fracturing on a hard and thick rock stratum directly above a cross-over layer by constructing an L-shaped horizontal well on the ground, and performing hydraulic fracturing on a top plate in an underground roadway, so that all rock strata below a key rock stratum of a coal face can be regularly collapsed, the hard top plate is integrally weakened, dynamic load generated by rock stratum fracture is reduced, and rock burst is treated from the source.

Drawings

FIG. 1 is an implementation state diagram of a method for preventing rock burst by hydraulic fracturing on an upper coal mine and a lower coal mine;

fig. 2 is a left side sectional view of fig. 1.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The invention provides a method for preventing rock burst by hydraulic fracturing of an upper part and a lower part of a coal mine, which comprises the following steps:

step 1, determining a coal face overlying rock key layer and a direct caving layer according to a mine geological comprehensive histogram, a microseismic event seismic source position, three-zone observation of adjacent stope faces and a key layer theory, further determining a hard thick rock layer between the coal face overlying rock key layer and the direct caving layer as a ground horizontal well fracturing layer, and determining the direct caving layer as an underground roof hydraulic fracturing layer;

step 2, constructing an L-shaped horizontal well on the ground to perform staged fracturing on a ground horizontal well fracturing layer, and specifically comprising the following steps as shown in figure 1:

step 2.1, constructing a vertical shaft section, and sleeving to reinforce a well mouth after completion;

2.2, constructing the vertical shaft to a position 30-100 m above a fracturing layer of the horizontal well on the ground, and starting deflecting;

2.3, adopting a directional system to horizontally drill in a fracturing layer of the horizontal well on the ground, and withdrawing the drill rod after drilling to a specified position;

and 2.4, performing hydraulic fracturing on the horizontal section, lowering the packer or the bridge plug, injecting high-pressure water into the two-stage packer or the bridge plug for fracturing, performing the fracturing integrally in a retreating mode, and continuously injecting fracturing fluid, fine sand and other fracture propping agents in the fracturing process until the fracturing of the horizontal section of the fracturing layer of the ground horizontal well is completed.

Step 3, performing hydraulic fracturing on the underground roof hydraulic fracturing layer by the advanced coal face before stoping of the coal face, so that all rock stratums below the key layer of the overlying rock of the coal face regularly collapse, and the method specifically comprises the following steps:

step 3.1, as shown in figure 2, drilling holes at the hydraulic fracturing layer position of the underground roof from the part above the waist line of the roadway coal wall of the advanced coal face of 300m, wherein the inclination angle is 20-50 degrees, and the construction, drainage and slag discharge are facilitated;

step 3.2, determining the fracturing times according to the structure of the top plate rock stratum and the thickness of the rock stratum, gradually fracturing from the bottom of a drill hole to an orifice, wherein the fracturing interval is 5m, modifying and adjusting the hole depth, the water pressure and the angle parameters of the underground top plate hydraulic fracturing according to the number of microseismic events and the positions of seismic sources, maintaining the stable pressure of a fracturing curve, and stopping fracturing operation after the pressure of the fracturing curve is obviously reduced;

and 3.3, determining the distance between the underground hydraulic fracturing drilling holes as the periodic pressure step distance of the working face, and repeating the steps 3.1-3.2 until the coal face is fractured to a coal mining stopping line.

Through the mode, the method for preventing and treating rock burst through hydraulic fracturing of the coal mine underground and the underground is used for performing staged fracturing on the hard and thick rock stratum above the directly-crossing rock stratum by constructing the L-shaped horizontal well on the ground, and performing hydraulic fracturing on the top plate in the underground roadway, so that all rock strata below the rock-covered key layer of the coal face can regularly collapse, the hard top plate is integrally weakened, dynamic load generated by rock stratum fracture is reduced, and the rock burst is treated from the source. The method has the following characteristics:

1. the invention is a regional measure for preventing and controlling rock burst, has obvious pressure relief effect and can realize the control of rock burst from the source;

2. hydraulic fracturing is adopted both above and below the well, so that the safety is high;

3. the fracturing range is wide, and the direct caving layer and the hard thick rock stratum below the key layer of the coal face are included.