1. A method for preventing rock burst by staged fracturing of an L-shaped ground horizontal well is characterized by comprising the following steps of:

step 1, determining a fracturing position and a fracturing distance;

step 2, constructing an L-shaped horizontal well vertical section on the ground, and embedding a sleeve to fix a well wall;

step 3, starting deflecting at a design point A and extending to a fracturing layer, and starting constructing a horizontal section of the 1# well when drilling to the horizontal direction;

step 4, adopting a retreating type fracturing 1# well horizontal section;

step 5, after fracturing of the horizontal section of the 1# well is completed, plugging the deflecting section of the 1# well, then extending the vertical well, beginning reverse deflecting at a position which is not less than 10m below a design point A and extending to a fracturing layer, and beginning construction of the horizontal section of the 2# well when drilling to the horizontal direction;

and 6, adopting a retreating type fracturing 2# well horizontal section.

2. The method for preventing and treating rock burst by staged fracturing of the L-shaped ground horizontal well according to claim 1, wherein in the step 1, the key layer of the coal face is determined according to a mine geological comprehensive histogram, three-zone observation of an adjacent working face, theoretical calculation and numerical simulation, the direct cross-over layer is determined according to the mine geological comprehensive histogram, a microseismic event and a seismic source position, and then a rock stratum between the key layer and the direct collapse layer is selected to be determined as the fracturing horizon.

3. The method for preventing and treating rock burst by staged fracturing of the L-shaped ground horizontal well according to claim 1, wherein the caving step of the rock stratum above the coal stratum top plate of the coal face is determined according to the number of microseismic events and the working resistance of the hydraulic support of the working face in the step 1, and the fracturing step is determined to be 1/2-1/3 of the caving step.

4. The method for preventing and treating rock burst by staged fracturing of an L-shaped horizontal ground well according to claim 1, wherein the step 4 specifically comprises the following steps:

4.1, ejecting 4-6 cluster perforations around the hole wall by using a perforating bullet at a fracturing position;

4.2, arranging 2 bridge plugs in the range of 20-50 m before and after the shower hole for plugging;

4.3, injecting high-pressure water into the 2 bridge plugs, and performing 360-degree fracturing on the high-pressure water through a perforation;

and 4.4, after fracturing one section, repeating the steps 4.1-4.3 at the next fracturing position until fracturing the horizontal section of the 1# well.

5. The method for preventing and treating rock burst by staged fracturing of an L-shaped horizontal ground well according to claim 4, wherein the retreating fracturing mode of the horizontal section of the No. 2 well is the same as that of the horizontal section of the No. 1 well.

Background

Rock burst is one of the main disasters faced by coal mining of deep mines, is getting more and more intense in China in recent years, and causes immeasurable loss to mines and personnel. According to statistics, the roof type rock burst of the deep mine coal face accounts for more than three quarters of the accidents of the roof type rock burst of the coal face, the main inducing factors of the roof type rock burst of the coal face are that large dynamic load is generated by sudden falling of a large-area suspended roof of a hard thick rock layer above a coal seam roof, and the high static load of a superposed working face induces the roof type rock burst of the coal face, so that how to avoid the large-area suspended roof of the hard roof of the coal face becomes the main research direction for solving the roof type rock burst.

Disclosure of Invention

The invention aims to provide a method for preventing rock burst by staged fracturing of an L-shaped ground horizontal well, which solves the problem that rock burst of a coal face is induced by sudden falling of a large-area suspended ceiling of a hard top plate of the existing coal face.

The technical scheme adopted by the invention is as follows: a method for preventing rock burst of an L-shaped ground horizontal well by staged fracturing comprises the following steps:

step 1, determining a fracturing position and a fracturing distance;

step 2, constructing an L-shaped horizontal well vertical section on the ground, and embedding a sleeve to fix a well wall;

step 3, starting deflecting at a design point A and extending to a fracturing layer, and starting constructing a horizontal section of the 1# well when drilling to the horizontal direction;

step 4, adopting a retreating type fracturing 1# well horizontal section;

step 5, after fracturing of the horizontal section of the 1# well is completed, plugging the deflecting section of the 1# well, then extending the vertical well, beginning reverse deflecting at a position which is not less than 10m below a design point A and extending to a fracturing layer, and beginning construction of the horizontal section of the 2# well when drilling to the horizontal direction;

and 6, adopting a retreating type fracturing 2# well horizontal section.

The present invention is also characterized in that,

in the step 1, a key layer of a coal face is determined according to a mine geological comprehensive histogram, three-zone observation of an adjacent working face, theoretical calculation and numerical simulation, a direct caving layer is determined according to the mine geological comprehensive histogram, a microseismic event and a seismic source position, and then a rock stratum between the key layer and the direct caving layer is selected to be determined as a fracturing layer.

In the step 1, the caving step of a rock stratum above a coal layer top plate of the coal face is determined according to the number of microseismic events and the working resistance of a hydraulic support of the working face, and the fracturing step is determined to be 1/2-1/3 of the caving step.

The step 4 specifically comprises the following steps:

4.1, ejecting 4-6 cluster perforations around the hole wall by using a perforating bullet at a fracturing position;

4.2, arranging 2 bridge plugs in the range of 20-50 m before and after the shower hole for plugging;

4.3, injecting high-pressure water into the 2 bridge plugs, and performing 360-degree fracturing on the high-pressure water through a perforation;

and 4.4, after fracturing one section, repeating the steps 4.1-4.3 at the next fracturing position until fracturing the horizontal section of the 1# well.

The retreating type fracturing mode of the 2# well horizontal section is the same as that of the 1# well horizontal section.

The invention has the beneficial effects that: the invention discloses a method for preventing rock burst by staged fracturing of an L-shaped ground horizontal well, which is characterized in that high-pressure hydraulic staged fracturing is carried out on a hard and difficult-to-collapse rock stratum covered on a coal face to enable the rock stratum to collapse regularly, so that the rock stratum large-area suspended ceiling suddenly strides and falls to avoid inducing the rock burst of the coal face, and the safe and efficient mining of a mine is realized.

Drawings

FIG. 1 is an implementation state diagram of a method for preventing rock burst by staged fracturing of an L-shaped ground horizontal well according to the invention;

FIG. 2 is a local state diagram of a deflecting section in the method for preventing and treating rock burst by staged fracturing of an L-shaped ground horizontal well.

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 and controlling rock burst by staged fracturing of an L-shaped horizontal well on ground, which comprises the following steps as shown in figures 1 and 2:

step 1, determining a key layer of a coal face through a mine geological comprehensive histogram, three-zone observation (a caving zone, a fissure zone and a bending subsidence zone) of an adjacent working face, theoretical calculation and numerical simulation, determining a direct caving layer according to the mine geological comprehensive histogram, a microseismic event and a seismic source position, and then selecting a hard thick rock stratum between the key layer and the direct caving layer to determine the hard thick rock stratum as a fracturing layer; determining the caving step of a hard thick rock layer above a coal layer top plate of a coal face according to the number of microseismic events and the working resistance of a hydraulic support of the working face, wherein the fracturing step is determined to be 1/2-1/3 of the caving step;

step 2, finishing a road surface, erecting a derrick, constructing an L-shaped horizontal well vertical section on the ground, and embedding a sleeve to fix a well wall to prevent underground water from invading the well wall;

step 3, after the construction of the vertical shaft section is finished, the deviation is started at a design point A, the drill bit is accurately controlled to accurately drill along the deviation making section by utilizing the comprehensive geological guiding drilling technology, the horizontal drilling is continued according to the length of the designed horizontal section after the horizontal landing of the target rock stratum fracturing section, and the construction of the horizontal section of the No. 1 well is started;

and 4, after the horizontal section construction of the 1# well is completed, performing staged fracturing on the target rock stratum by using high-pressure water. The hydraulic fracturing adopts a retreating type, and specifically comprises the following steps:

4.1, ejecting 4-6 cluster perforations around the hole wall by using a perforating bullet at a fracturing position;

4.2, arranging 2 bridge plugs for plugging within the range of 20-50 m (based on the fracture spacing not exceeding) before and after the shower hole;

4.3, injecting high-pressure water into the 2 bridge plugs, and performing 360-degree fracturing on the high-pressure water through a perforation;

4.4, after fracturing one section, repeating the steps 4.1-4.3 at the next fracturing position until fracturing the horizontal section of the 1# well;

step 5, after fracturing of the horizontal section of the 1# well is completed, plugging the deflecting section of the 1# well, then extending the vertical well, beginning reverse deflecting at a position which is not less than 10m below a design point A and extending to a fracturing layer, and beginning construction of the horizontal section of the 2# well in the same way as the 1# well when drilling to the horizontal direction;

and 6, after the construction of the horizontal section of the 2# well is finished, repeating the step 4 and fracturing the horizontal section of the 2# well in a retreating mode until all the horizontal sections of the 2# well are fractured.

Through the mode, the method for preventing rock burst through staged fracturing of the L-shaped ground horizontal well disclosed by the invention has the advantages that the rock stratum which is covered on the coal face and hard and difficult to collapse is subjected to high-pressure hydraulic staged fracturing, so that the rock stratum is regularly collapsed, the rock stratum is prevented from suddenly striding over a large area of a suspended roof to induce the rock burst of the coal face, and the safe and efficient mining of a mine is realized. Still possess following characteristics:

1. all the equipment related by the invention is on the ground, and compared with underground construction, the size, power and number of the equipment are not limited, and the construction can be better, faster and more economic.

2. Compared with conventional blasting pressure relief, the hydraulic fracturing is safer.

3. The dual-purpose vertical shaft has the advantages that the dual-purpose vertical shaft is realized, 2L-shaped horizontal wells in different directions are constructed by repeatedly utilizing the vertical shaft section, and the economical efficiency is better.