Method for preventing outbursts in advance in the initial mining area of ​​the outburst coal seam working face

Abstract

The present invention relates to a method for pre-draining and preventing outbursts in the initial mining area of ​​a coal seam working face, and belongs to the field of coal and gas outburst prevention and control in coal mines. It includes steps S1, designing a directional branch long drill hole on the coal seam roof; S2, constructing a directional branch long drill hole on the coal seam roof, and performing segmented hydraulic fracturing on it; S3, connecting to the extraction pipeline for gas extraction. The present invention solves the technical problems of large outburst prevention engineering volume, high cost, short outburst prevention time, and influence on mining and excavation succession in the initial mining area of ​​the working face. The directional branch long drill hole on the coal seam roof is combined with hydraulic fracturing technology to realize pre-draining and preventing outbursts in the initial mining area of ​​the mining working face, which is of great significance to reducing the cost of preventing outbursts, realizing rapid succession of mining and excavation on the working face, and improving the production capacity of the mine.

Description

Technical Field

[0001] The invention belongs to the field of coal and gas outburst prevention and control in coal mines, and specifically relates to an advance pre-drainage outburst prevention method in the initial mining area of ​​a working face of an outburst coal seam. Background Art

[0002] Coal and gas outburst (abbreviated as "outburst") disaster ranks first among the five major disasters in coal mines. At present, the prevention and control of outburst disasters is still a global problem. At present, my country has established two "four-in-one" comprehensive outburst prevention technology systems, namely regional and local. Among them, the coal roadway strip mainly adopts the roof rock roadway combined with through-layer drilling extraction for regional outburst prevention. This method has a relatively significant effect in preventing outbursts, but the construction of rock roadways and drilling holes is large in quantity and time, which affects the succession of mining and excavation. In addition, the prevention time of outbursts near the cutting eye of the mining face (also called the starting mining area of ​​the working face) is short. If the prevention effect is not achieved, the mining face cannot continue to be mined, which seriously restricts the succession of mining and excavation and becomes the "shortest board" problem of outburst prevention of the mining face. In order to solve this problem, the boundary (return air) is often designed to go downhill at the boundary of the mining area to prevent outbursts in the cutting eye area of ​​the mining face in advance. This method has a good effect in preventing outbursts, but it has a large amount of work and high cost. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a method for advance pre-drainage and prevention of coal seam outbursts in the initial mining area of ​​the working face, so as to solve the technical problems existing in the initial mining area of ​​the working face, such as large amount of outburst prevention engineering, high cost, short outburst prevention time, and impact on mining succession.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A method for preventing coal outbursts in advance in the initial mining area of ​​a coal seam working face, comprising the following steps: S1, designing a directional branch long drill hole on the coal seam roof; S2, constructing a directional branch long drill hole on the coal seam roof, and performing segmented hydraulic fracturing on the hole; S3, connecting a drainage pipeline to perform gas drainage;

[0006] In step S1, the directional branch long drilling holes in the coal seam roof include main holes and branch holes, and the branch holes are symmetrically distributed along both sides of each main hole;

[0007] The construction parameters of the main hole include the construction position in the strike direction of the coal seam, the construction layer in the vertical direction, and the construction length in the dip direction;

[0008] Among them, in the direction of the coal seam, the construction position L1 of the first main hole is:

[0009] L1=Y1+r-L2;

[0010] Where: Y1 is the length of the branch hole control area projected in the horizontal direction, in m; r is the hydraulic fracturing radius of the branch hole, in m; L2 is the control width outside the outer contour line of the roadway of the mining face cut, in m;

[0011] The construction position L of the nth main hole n for:

[0012] L n =(Y1+r-L2)+(n-1)×△L;

[0013] Where: △L is the distance between the nth main hole and its adjacent main hole, in m; n is the main hole number, n≥2;

[0014] In the coal seam dip direction, the roof rock tunnel is arranged in the middle of the mining area, and the main holes are symmetrically distributed on both sides of the roof rock tunnel with the roof rock tunnel as the symmetry axis; the construction length X of each main hole in the coal seam dip direction is:

[0015] X=X0+X1+X2+…+X n +(n-1)×d+L3;

[0016] Where: X0 is the horizontal distance between the roof rock tunnel and the first mining face, in m; X1 is the sum of the width of the transport tunnel, the length of the cut hole, and the width of the return air tunnel of the first mining face, in m; X2 is the sum of the width of the transport tunnel, the length of the cut hole, and the width of the return air tunnel of the second mining face, in m; X n is the sum of the width of the transport lane, the length of the cut eye, and the width of the return air lane of the nth mining face, in m; d is the width of the coal pillar, in m; L3 is the control width between the outer contour line of the outermost lane of the nth mining face and the boundary line of the extraction control area, in m;

[0017] In step S3, the time required from the start of construction of the directional branch long drilling hole in the coal seam roof to the achievement of extraction standards and qualified effect inspection in the starting area of ​​the mining face should be less than or equal to the sum of the time required for the construction of the roof rock roadway, the extraction drilling hole construction, the drilling gas extraction standard time and the coal roadway excavation of the same mining face.

[0018] Furthermore, in step S1, in the direction of the coal seam strike, the length of the extraction area of ​​the starting area of ​​the mining face controlled by the main hole and the branch hole is not less than 300m.

[0019] Furthermore, in step S1, the construction layer of the main hole in the vertical direction is 1 to 5 meters above the coal seam roof rock layer.

[0020] Further, in step S1, in the direction of the coal seam strike, the length Y1 of the branch hole control area projected in the horizontal direction is 50 to 100 m.

[0021] Furthermore, in step S2, the main hole is constructed first, and when the main hole construction reaches a predetermined depth, the branch holes are constructed in sequence at intervals L from the bottom of the main hole to the hole mouth.

[0022] Furthermore, in step S2, each branch hole is divided into a segment and hydraulic fracturing is performed on the branch holes in segments.

[0023] Furthermore, in step S3, the directional branch long drill holes in the coal seam roof constructed in each mining face are connected to the extraction pipeline for extraction, and the gas extraction volume is measured separately. Then, the gas extraction compliance is judged based on the gas extraction volume. Mining operations can only be carried out when the gas extraction in the extraction area of ​​the mining face meets the standards.

[0024] The beneficial effects of the present invention are:

[0025] The present invention solves the technical problems of large amount of anti-burst engineering work, high cost, short anti-burst time and influence on mining succession in the initial mining area of ​​the working face. The invention adopts directional branch long drilling of coal seam roof combined with hydraulic fracturing technology to realize advance pre-drainage and anti-burst in the initial mining area of ​​the recovery working face, which is of great significance to reducing the cost of anti-burst, realizing rapid succession of mining on the working face and improving the production capacity of the mine.

[0026] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0028] Figure 1 It is a schematic diagram of the plan layout of the method of pre-extraction and outburst prevention in the initial mining area of ​​the outburst coal seam working face;

[0029] Figure 2 It is a schematic diagram of the cross-sectional arrangement of the directional branch long boreholes in the coal seam roof in the direction of the coal seam strike;

[0030] Figure 3 It is a schematic diagram of the cross-sectional arrangement of the directional branch long boreholes in the coal seam roof in the coal seam dip direction;

[0031] Figure 4 Schematic diagram of the directional branch long drilling segmented hydraulic fracturing process in the coal seam roof.

[0032] Reference numerals:

[0033] 1- Roof slate alley;

[0034] 2- Transportation tunnel of mining working face;

[0035] 3-Return air lane of mining working face;

[0036] 4- Cutting of the mining face;

[0037] 5- Main hole of directional branch long drilling in coal seam roof;

[0038] 6-Branch holes of directional branch long drilling holes in the coal seam roof;

[0039] 7-Boundary line of the extraction control area of ​​the directional branch long borehole in the coal seam roof;

[0040] 8- Coal seam;

[0041] 9- Extraction pipeline;

[0042] 10-front packer;

[0043] 11- rear packer;

[0044] 12-Up and downhill tunnels in the mining area;

[0045] Y1-the length of the horizontal projection of the branch hole control area;

[0046] r-hydraulic fracturing radius of branch holes;

[0047] h-the construction layer of the main hole in the vertical direction;

[0048] L1-the horizontal distance between the first main hole and the outer contour line of the cut of the corresponding mining face;

[0049] L2-the control width between the outer contour line of the roadway of the mining face and the boundary line of the extraction control area;

[0050] L3-the control width between the outer contour line of the outermost roadway of the nth mining face and the boundary line of the extraction control area;

[0051] △L-the distance between the main hole and its adjacent main hole;

[0052] L- construction distance between two adjacent branch holes;

[0053] X0-horizontal distance between the roof rock tunnel and the first mining working face;

[0054] X1-the sum of the width of the transport lane, the length of the cut eye and the width of the return air lane of the first mining face;

[0055] X2-the sum of the width of the transport lane, the length of the cut eye and the width of the return air lane of the second mining face;

[0056] Xn -The sum of the width of the transport lane, the length of the cut eye and the width of the return air lane of the nth mining face;

[0057] X-the construction length of the main hole in the coal seam dip direction;

[0058] d-Width of coal pillar. DETAILED DESCRIPTION

[0059] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0060] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0061] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0062] See also Figure 1 to Figure 3 , which is a method for preventing coal outbursts in advance in the initial mining area of ​​a coal seam working face, and specifically includes the following steps:

[0063] Step 1: Design directional branch long boreholes in the coal seam roof.

[0064] The directional branch long drilling holes in the coal seam roof include a main hole 5 and a branch hole 6. The construction parameters of the main hole 5 and the branch hole 6 are designed respectively. The specific implementation method is described in detail as follows:

[0065] (1) Design construction parameters of main hole 5

[0066] The construction parameters of the main hole 5 mainly include the construction position in the direction of the coal seam strike, the construction layer in the vertical direction and the construction length in the dip direction, which are determined as follows:

[0067] 1) Construction location in the direction of the coal seam

[0068] Reference Figure 1 , Figure 3 According to the requirements of gas control, gas pre-extraction is required at least within L2 outside the outer contour of the roadway of the mining face cut 4 to eliminate the danger of outburst, and L2 is generally not less than 20m. Assuming that the horizontal projection length of the branch hole control area of ​​the directional branch long drilling hole in the coal seam roof is Y1, the hydraulic fracturing radius of the branch hole 6 is r, and the mining face cut 4 is taken as the reference point, the construction position L1 of the first main hole in the direction of the coal seam strike is:

[0069] L1=Y1+r-L2;

[0070] Wherein: L1 is the horizontal distance between the first main hole and the outer contour line of the corresponding mining face cut, in m; Y1 is the length of the branch hole control area projected in the horizontal direction, in m; r is the hydraulic fracturing radius of the branch hole, in m; L2 is the control width outside the outer contour line of the tunnel of the mining face cut (between the boundary line 7 of the extraction control area), in m.

[0071] Since the hydraulic fracturing radius of the branch hole 6 is r, the spacing between two adjacent main holes (i.e., the second, third, ..., n-1th and nth main holes) should be less than or equal to 2 times the hydraulic fracturing radius r of the branch hole 6 to meet the requirements of preventing outbursts and facilitate hydraulic fracturing. Therefore, starting from the second main hole, the construction spacing △L of the main hole 5 in the direction of the coal seam should satisfy: △L≤2Y1+2r; therefore, the construction position of the nth main hole is:

[0072] L n =(Y1+r-L2)+(n-1)×△L;

[0073] Where: △L is the distance between the main hole and its adjacent main hole, in meters; n is the main hole number, n≥2.

[0074] Reference Figure 1 According to the effect inspection of the mining face and the evaluation requirements of gas extraction compliance, in the direction of the coal seam strike, the length of the extraction area of ​​the starting area of ​​the mining face controlled by the main hole 5 shall not be less than 300m, that is, the length of the extraction area covered by the main hole 5 and the branch hole 6 in the strike direction shall be greater than or equal to 300m.

[0075] 2) Construction layer in the vertical direction

[0076] In view of the relatively poor porosity of the coal seam 8 (especially the soft coal seam), in order to ensure the construction length of the main hole 5, the main hole 5 is generally arranged 1 to 5 meters above the roof rock layer of the coal seam.

[0077] 3) Construction length in the direction of coal seam dip

[0078] Reference Figure 1 According to the mining area design, in the coal seam dip direction, the roof rock tunnel 1 is arranged in the middle of the mining area, and the main holes 5 of the directional branch long drill holes in the coal seam roof are symmetrically distributed with the roof rock tunnel 1 as the symmetry axis; this arrangement can carry out large-area pre-extraction of the mining working faces on both sides, thereby improving the efficiency and effect of preventing outbursts.

[0079] Assume that there are n mining faces on both sides of the roof rock tunnel 1, and the lengths corresponding to the mining faces (specifically, the sum of the width of the transport tunnel, the length of the cut hole, and the width of the return air tunnel of the mining face) are X1, X2, ..., X n , the width of each coal pillar is the same, that is, d, then the main hole should pass through the outermost tunnel of the nth mining face (i.e. Figure 1 The outer contour line of the return air lane 3 of the mining working face is L3 above, and L3 is generally not less than 15m; then the construction length X of the main hole 5 in the coal seam dip direction is:

[0080] X=X0+X1+X2+…+X n +(n-1)×d+L3;

[0081] Where: X0 is the horizontal distance between the roof rock tunnel and the first mining face, in m; X1 is the sum of the width of the transport tunnel, the length of the cut hole, and the width of the return air tunnel of the first mining face, in m; X2 is the sum of the width of the transport tunnel, the length of the cut hole, and the width of the return air tunnel of the second mining face, in m; X n It is the sum of the width of the transport tunnel, the length of the cutting eye and the width of the return air tunnel of the nth mining face, in m; d is the width of the coal pillar, in m; L3 is the control width between the outer contour line of the outermost tunnel of the nth mining face and the boundary line 7 of the extraction control area, in m.

[0082] (2) Design construction parameters of branch hole 6

[0083] The branch holes 6 are symmetrically distributed along both sides of each main hole 5, and their construction parameters mainly include the construction position in the strike direction, the horizontal projection length in the strike direction, and the construction spacing in the dip direction.

[0084] In the direction of the coal seam, the construction position of the branch hole 6 is the same as that of the main hole 5, which will not be repeated here.

[0085] In the direction of the coal seam strike, the horizontal projection length Y1 of the branch hole 6 is designed according to the occurrence of the coal seam, and Y1 is generally 50 to 100 m.

[0086] In the dip direction of the coal seam, the construction spacing L between two adjacent branch holes 6 is designed according to the hydraulic fracturing radius r of the coal seam. L is generally not greater than twice the hydraulic fracturing radius r, that is, L≤2r.

[0087] Step 2: Construct directional branch long boreholes in the coal seam roof and perform segmented hydraulic fracturing on the branch holes.

[0088] After the construction parameters of the main hole 5 and the branch hole 6 are designed, the construction is carried out according to the designed parameters. The main hole 5 is constructed first, and when the main hole 5 reaches a predetermined depth, the branch holes 6 are constructed in sequence from the bottom of the main hole to the hole mouth at intervals L.

[0089] Reference Figure 4 In order to ensure the gas extraction effect, each branch hole is divided into a segment and hydraulic fracturing is performed on the branch hole 6 in segments.

[0090] Step 3: Connect the extraction pipeline 9 to extract gas.

[0091] Reference Figure 1 The long directional branch boreholes in the coal seam roof constructed in each mining face are connected to the extraction pipeline 9 for extraction, and the gas extraction volume is measured separately. Then, the gas extraction compliance is evaluated based on the gas extraction volume. Mining operations can only be carried out when the gas extraction in the extraction area of ​​the working face meets the standards.

[0092] In order to achieve advance pre-drainage and prevention of outbursts in the starting mining area of ​​the coal seam working face, it is necessary to ensure that the time required from the start of construction of the directional branch long drilling hole in the coal seam roof to the extraction reaching the standard and the qualified effect inspection in the starting mining area of ​​the mining face is less than or equal to the sum of the time required for the construction of the roof rock roadway, the extraction drilling hole construction, the drilling gas extraction reaching the standard time and the coal roadway excavation of the same mining face. The calculation formula is:

[0093] T s +T d ≤T y +T k +T c +T m ;

[0094] Where: T s The time required for the directional branch long drilling construction of the coal seam roof in the initial mining area of ​​the mining face, in days; T d It is the time required for the coal seam extraction in the initial mining area of ​​the mining face to meet the standards and the effect inspection to be qualified, in "days"; T y T is the time required for excavation of the top slate roadway of the mining face, in days; kT is the time required for the construction of extraction drilling holes in the return air lane and the transport lane of the mining face, in days; c It is the time required for the return air lane and the transport lane of the mining face to meet the extraction standards and pass the effect inspection, in "days"; T m It is the time required to complete the return air tunnel, transport tunnel and eye cutting excavation of the mining face, and the unit is "day".

[0095] By rationally controlling the time according to this formula, advance pre-drainage and outburst prevention can be achieved in the initial mining area of ​​the outburst coal seam working face.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preventing coal outbursts in advance in the initial mining area of ​​a coal seam working face, characterized in that The following steps are involved: S1. Design directional branch long drilling holes in the coal seam roof; S2, constructing a directional branch long borehole in the coal seam roof and performing segmented hydraulic fracturing on it; S3, connecting to the extraction pipeline (9) for gas extraction; In step S1, the directional branch long drilling holes in the coal seam roof include a main hole (5) and branch holes (6), and the branch holes (6) are symmetrically distributed along both sides of each main hole (5); The construction parameters of the main hole (5) include the construction position in the strike direction of the coal seam, the construction layer position in the vertical direction, and the construction length in the dip direction; Among them, in the direction of the coal seam, the construction position L1 of the first main hole is: L1=Y1+r-L2; Where: Y1 is the length of the branch hole control area projected in the horizontal direction, in m; r is the hydraulic fracturing radius of the branch hole, in m; L2 is the control width outside the outer contour line of the roadway of the mining face cut, in m; The construction position L of the nth main hole n for: <h2 style=";text-align:left;direction:ltr">L<h2 style=";text-align:left;direction:ltr"> n <h2 style=";text-align:left;direction:ltr"> =(Y1+r-L2)+(n-1)×△L; Where: △L is the distance between the nth main hole and its adjacent main hole, in m; n is the main hole number, n≥2; In the coal seam dip direction, the roof rock tunnel (1) is arranged in the middle of the mining area, and the main holes (5) are symmetrically distributed on both sides of the roof rock tunnel (1) with the roof rock tunnel (1) as the symmetry axis; the construction length X of each main hole (5) in the coal seam dip direction is: X=X0+X1+X2+…+X n +(n-1)×d+L3; Where: X0 is the horizontal distance between the roof rock tunnel and the first mining face, in m; X1 is the sum of the width of the transport tunnel, the length of the cut hole, and the width of the return air tunnel of the first mining face, in m; X2 is the sum of the width of the transport tunnel, the length of the cut hole, and the width of the return air tunnel of the second mining face, in m; X n is the sum of the width of the transport lane, the length of the cut eye, and the width of the return air lane of the nth mining face, in m; d is the width of the coal pillar, in m; L3 is the control width between the outer contour line of the outermost lane of the nth mining face and the boundary line of the extraction control area, in m; In step S3, the time required from the start of construction of the directional branch long drilling hole in the coal seam roof in the starting area of ​​the mining face to the achievement of extraction standards and qualified effect inspection should be less than or equal to the sum of the time required for the construction of the roof rock roadway, extraction drilling construction, the achievement of drilling gas extraction standards and the coal roadway excavation of the same mining face.

2. The method for preventing outbursts in the initial mining area of ​​the outburst coal seam working face according to claim 1 is characterized by: In step S1, in the direction of the coal seam, the length of the extraction area of ​​the starting area of ​​the mining face controlled by the main hole (5) and the branch hole (6) is not less than 300m.

3. The method for preventing outbursts in the initial mining area of ​​an outburst coal seam working face according to claim 1 is characterized in that: In step S1, the construction layer of the main hole (5) in the vertical direction is 1 to 5 meters above the roof rock layer of the coal seam (8).

4. The method for preventing outbursts in the initial mining area of ​​an outburst coal seam working face according to claim 1 is characterized in that: In step S1, in the direction of the coal seam strike, the length Y1 of the horizontal projection of the branch hole (6) control area is 50 to 100 m.

5. The method for preventing outbursts in the initial mining area of ​​an outburst coal seam working face according to claim 1 is characterized in that: In step S2, the main hole (5) is constructed first, and when the main hole (5) reaches a predetermined depth, the branch holes (6) are constructed in sequence at intervals L from the bottom of the main hole to the hole mouth.

6. The method for preventing outbursts in the initial mining area of ​​an outburst coal seam working face according to claim 1 is characterized by: In step S2, each interval of a plurality of branch holes (6) is a segment, and the branch holes (6) are hydraulically fractured in segments.

7. The method for preventing outbursts in the initial mining area of ​​an outburst coal seam working face according to claim 1 is characterized by: In step S3, the directional branch long boreholes of the coal seam roof constructed in each mining face are connected to the extraction pipeline (9) for extraction, and the gas extraction volume is measured separately. Then, the gas extraction compliance is evaluated based on the gas extraction volume. Mining operations can only be carried out when the gas extraction in the extraction area of ​​the mining face meets the compliance.

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