A method for pre-controlling local de-shock of downhole long borehole directional fracturing

Abstract

The application provides a method for local shock elimination and pre-control of long borehole directional fracturing in a mine, which comprises the following steps: taking core test of target coal seams and roof and floor strata; establishing a numerical simulation model of the target coal seam mining, and obtaining stress concentration characteristics of strata within a range of 50m normal distance of the target coal seam; recording the normal distance of the stratum with the highest stress concentration coefficient from the target coal seam and the dip angle of the target coal seam; arranging fracturing holes in the strata to be fractured at certain intervals along the strata dip direction; and drilling and fracturing according to the positions of the fracturing holes. The application obtains the stress concentration characteristics of the coal seam through numerical simulation, determines the stratum with the highest stress concentration coefficient, records the normal distance of the stratum from the coal seam and the dip angle of the coal seam, then arranges fracturing holes in the strata to be fractured at certain intervals, and finally drills and fractures according to the design, so that the coal seam shock is eliminated, and the safety production of the mine is ensured.

Description

Technical Field

[0001] This invention relates to the field of rockburst technology, and in particular to a method for local rockburst mitigation and pre-control of directional fracturing in long downhole boreholes. Background Technology

[0002] Rockburst is a disaster caused by the instantaneous release of elastic energy accumulated in coal and rock mass due to disturbance during mining, resulting in damage to the surrounding rock or strong vibrations in the mining space. To date, the main methods for rockburst prevention and control internationally are "local rockburst prevention" technologies such as coal seam drilling for pressure relief, blasting for pressure relief, water injection, and roof cutting. Although these methods have achieved certain results, they involve a large amount of technical engineering, are costly, have significant human impact, and their effectiveness cannot be guaranteed, leading to the continuous occurrence of rockburst accidents. "Regional rockburst prevention" methods mainly involve mining the release layer. However, in mining areas where there is no release layer or where mining the release layer is difficult, there is currently no effective regional rockburst prevention technology.

[0003] Rockbursts in mines have been a major concern since their inception due to their immense destructive power and the potential economic losses and even casualties they can cause. Field practice has shown that, based on a correct understanding of the mechanisms underlying rockbursts, targeted prevention and control measures often yield good results. The present invention introduces a local rockburst mitigation and pre-control technology using directional fracturing in long boreholes in underground mines. This technology primarily targets steeply inclined coal seams, strategically arranging fracturing holes to achieve localized elimination of rockbursts.

[0004] Therefore, how to eliminate the impact of rock bursts on mines and ensure safe production has become an urgent technical problem to be solved. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a method for local flushing control in directional fracturing of long downhole boreholes.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A method for local flushing control in directional fracturing of long downhole boreholes includes:

[0008] Core sampling was conducted on the target coal seam and the roof and floor strata to test the mechanical parameters of the coal and rock mass specimens.

[0009] Based on the geological conditions of the working face, a numerical simulation model for mining the target coal seam was established, and the stress concentration characteristics of the rock strata within a normal distance of 50m of the target coal seam were obtained.

[0010] Record the normal distance d from the rock stratum with the highest stress concentration characteristic coefficient to the target coal seam and the dip angle θ of the target coal seam;

[0011] The left and right sides of the drilling point in the tunnel are designated as regions A and B respectively. In region A, the angle between the top fracturing hole and the vertical direction is a1, and the angle between the bottom fracturing hole and the horizontal direction is a2. In region B, the angle between the top fracturing hole and the horizontal direction is a3, and the angle between the bottom fracturing hole and the vertical direction is a4.

[0012] Fracturing holes are arranged at regular intervals L along the dip direction of the rock stratum within the rock stratum to be fractured.

[0013] Drilling and fracturing processes are performed according to the location of the fracturing holes.

[0014] Preferably, the mechanical parameters include: compressive strength, tensile strength, cohesion, internal friction angle, and Poisson's ratio.

[0015] Preferably, the formulas for calculating the angles between the fracturing hole and the vertical and horizontal directions are as follows:

[0016]

[0017] Preferably, the formula for calculating L is:

[0018] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0019] This invention provides a method for local flushing and pre-control of directional fracturing in long-bore underground mines, comprising: core sampling and testing of the target coal seam and roof and floor strata to measure the mechanical parameters of the coal and rock mass specimens; establishing a numerical simulation model for mining the target coal seam based on the geological conditions of the working face, and obtaining the stress concentration characteristics of the strata within a 50m range of the target coal seam; recording the normal distance d of the strata with the highest stress concentration coefficient from the target coal seam and the dip angle θ of the target coal seam; designating the left and right sides of the borehole point in the roadway as regions A and B respectively; wherein the angle between the topmost fracturing hole and the vertical direction in region A is a1, and the angle between the bottommost fracturing hole and the horizontal direction is a2; the angle between the topmost fracturing hole and the horizontal direction in region B is a3, and the angle between the bottommost fracturing hole and the vertical direction is a4; arranging fracturing holes at regular intervals L along the dip direction of the strata within the rock strata to be fractured; and performing drilling and fracturing processes according to the positions of the fracturing holes. Based on the geological conditions and related parameters of a steeply inclined coal seam fully mechanized longwall face, this invention obtains the stress concentration characteristics of the coal seam through numerical simulation, identifies the rock stratum with the highest stress concentration coefficient, records its normal distance from the coal seam and the dip angle of the coal seam, then arranges fracturing holes at certain intervals in the rock stratum to be fractured, and finally carries out the drilling and fracturing process according to the design, thereby eliminating rockburst in the coal seam and ensuring safe production in the mine. Attached Figure Description

[0020] 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.

[0021] Figure 1 A flowchart of the method provided in an embodiment of the present invention;

[0022] Figure 2 This is a directional fracturing profile of a long downhole borehole provided in an embodiment of the present invention;

[0023] Explanation of reference numerals in the attached figures:

[0024] 1-The rock stratum to be fractured, 2-The target coal seam, 3-The fracture hole. Detailed Implementation

[0025] 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.

[0026] The purpose of this invention is to provide a localized anti-rock pressure control technology for directional fracturing in long downhole boreholes, which can locally eliminate rock pressure in coal and rock masses.

[0027] 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.

[0028] Figure 1 The method flowchart provided in the embodiments of the present invention is as follows: Figure 1 As shown, this invention provides a method for local flushing control in directional fracturing of long downhole boreholes, comprising:

[0029] Step 100: Conduct core sampling tests on the target coal seam and the roof and floor strata to test the mechanical parameters of the coal and rock mass specimens;

[0030] Step 200: Based on the geological conditions of the working face, establish a numerical simulation model for the mining of the target coal seam, and obtain the stress concentration characteristics of the rock strata within a normal distance of 50m from the target coal seam;

[0031] Step 300: Record the normal distance d from the rock stratum with the highest stress concentration characteristic coefficient to the target coal seam and the dip angle θ of the target coal seam;

[0032] Step 400: The left and right sides of the drilling point in the tunnel are designated as regions A and B respectively; the angle between the top of the fracturing hole and the vertical direction in region A is a1, and the angle between the bottom of the fracturing hole and the horizontal direction is a2; the angle between the top of the fracturing hole and the horizontal direction in region B is a3, and the angle between the bottom of the fracturing hole and the vertical direction is a4.

[0033] Step 500: Arrange fracturing holes at regular intervals L along the dip direction of the rock strata within the intended fracturing layer;

[0034] Step 600: Perform drilling and fracturing processes according to the location of the fracturing holes.

[0035] The main steps of the local flushing process for long borehole fracturing in this embodiment are as follows:

[0036] a. On-site core sampling and testing of the target coal seam 2 and the roof and floor strata were conducted to test the compressive strength, tensile strength, cohesion, internal friction angle, Poisson's ratio and other mechanical parameters of the coal and rock mass specimens.

[0037] b. Based on the geological conditions of the working face, establish a numerical simulation model for coal seam mining and obtain the stress concentration characteristics of the rock strata within a 50m range of the target coal seam 2 in the normal direction;

[0038] c. Take the rock stratum with the highest stress concentration factor, and record its normal distance d from the coal seam and the dip angle θ of the target coal seam.

[0039] d. The left and right sides of the drilling point in the tunnel are respectively designated as regions A and B in the vertical direction.

[0040] e. In region A, the angle between the topmost fracturing hole 3 and the vertical direction is a1, and the angle between the bottommost fracturing hole 3 and the horizontal direction is a2; in region B, the angle between the topmost fracturing hole 3 and the horizontal direction is a3, and the angle between the bottommost fracturing hole 3 and the vertical direction is a4.

[0041] f. At regular intervals L within the rock stratum 1 to be fractured, fracture holes 3 are arranged along the dip direction of the rock stratum.

[0042] g. Perform drilling and fracturing processes according to the design.

[0043] in, θ is the dip angle of the coal seam;

[0044] Furthermore, In the formula, L is the distance between two adjacent fracturing holes 3 along the dip direction of the rock layer 1 to be fractured.

[0045] The local flushing reduction process for long borehole fracturing of the present invention is illustrated below using a coal mine in Shanxi Province as an example:

[0046] ① On-site core sampling and testing were conducted on the target coal seam 2 and the roof and floor strata to obtain mechanical parameters such as compressive strength, tensile strength, cohesion, internal friction angle, and Poisson's ratio of the coal and rock mass specimens.

[0047] ② Based on the geological conditions of the working face, establish a numerical simulation model for coal seam mining and obtain the stress concentration characteristics of the rock strata within a 50m range of the target coal seam 2 in the normal direction;

[0048] ③ According to the measurement, the normal distance between the rock layer with the highest stress concentration coefficient and the target coal seam 2 is d = 50m, and the dip angle of the target coal seam 2 is θ = 50°;

[0049] ④ The angle between the topmost fracturing hole 3 in area A and the vertical direction The angle between the bottom fracturing hole 3 and the horizontal direction The angle between the topmost fracturing hole 3 in area B and the horizontal direction is... The angle between the bottom fracturing hole 3 and the vertical direction

[0050]

[0051] ⑤ At regular intervals within the simulated fractured rock layer 1

[0052] Three fracturing holes are arranged along the dip direction of the rock strata.

[0053] ⑥ Carry out drilling and fracturing processes according to the design.

[0054] The beneficial effects of this invention are as follows:

[0055] The local flushing elimination process for long borehole fracturing provided by this invention can effectively improve the elimination effect of rockburst by reasonably segmenting the fracturing opening, avoid the danger caused by rockburst, make mine production safer and more reliable, and improve economic benefits.

[0056] 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.

[0057] 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 local flushing control in directional fracturing of long downhole boreholes, characterized in that, include: Core sampling was conducted on the target coal seam and the roof and floor strata to test the mechanical parameters of the coal and rock mass specimens. Based on the geological conditions of the working face, a numerical simulation model for mining the target coal seam was established, and the stress concentration characteristics of the rock strata within a normal distance of 50m of the target coal seam were obtained. Record the normal distance d from the rock stratum with the highest stress concentration characteristic coefficient to the target coal seam and the dip angle θ of the target coal seam; The left and right sides of the drilling point in the tunnel are designated as regions A and B, respectively; the angle between the topmost fracturing hole in region A and the vertical direction is... a 1. The angle between the lowest fracturing hole and the horizontal direction is... a 2; The angle between the fracturing hole at the top of region B and the horizontal direction is... a 3. The angle between the lowest fracturing hole and the vertical direction is... a 4; Within the rock stratum with the highest stress concentration coefficient, fracturing holes are arranged at regular intervals L along the dip direction of the rock stratum. Drilling and fracturing processes are performed according to the location of the fracturing holes; The formulas for calculating the angles between the fracturing hole and the vertical and horizontal directions are as follows: ， ， ， ； The formula for calculating L is: .

2. The method for local flushing reduction and pre-control of directional fracturing in long downhole boreholes according to claim 1, characterized in that, The mechanical parameters include: compressive strength, tensile strength, cohesion, internal friction angle, and Poisson's ratio.

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