Jet flow fracturing method for improving coal caving rate of hard and thick top coal fully mechanized caving face

Abstract

The invention relates to the technical field of coal mining, in particular to a jet fracturing method for improving the coal caving rate of a hard and thick top coal fully mechanized caving face, which comprises the following steps: constructing a first directional long drill hole in top coal; a plurality of second directional long drill holes are constructed in the top plate, and the drilling direction of the second directional long drill holes is perpendicular to the working face; based on the multiple second directional long drill holes, the top plate is subjected to jet fracturing; a rock block is formed on the top plate and acts on the top coal; and fracturing the top coal based on the first directional long drill hole. The method comprises the following steps: constructing a first directional long drill hole in top coal; a plurality of second directional long drill holes are constructed in the top plate, advanced drill holes are not affected by stoping, and crack expansion is more sufficient; based on the multiple second directional long drill holes, the top plate is subjected to jet fracturing; the rock block acts on the top coal, so that the weighting step pitch can be reduced, and the rock is broken and rotated in time and acts on the coal body; based on the first directional long drill hole, the top coal is fractured, and the density and complexity of the hydraulic fracture of the coal hole can be increased.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, and in particular to a jet fracturing method for improving the coal caving rate of a fully mechanized caving working face of hard and thick top coal. Background Art

[0002] Hard and thick top coal refers to the roof on the coal seam with high strength, high elastic modulus, large thickness, integral cavity and strong self-bearing capacity. After the coal seam is mined, the hard roof may be exposed over a large area without collapsing, resulting in large initial and periodic pressure steps on the working face and high pressure when the roof is pressed.

[0003] The top coal recovery rate is low in the fully mechanized caving working face with hard and thick top coal, which causes serious waste of coal resources and easily causes spontaneous combustion in the goaf. There are two reasons for this: first, the top coal itself is relatively hard, and second, the pressure on the working face is not obvious, especially at the two ends of the working face, where the top coal recovery rate is even lower. Therefore, it is necessary to weaken the top coal in advance.

[0004] In the prior art, the commonly used method of fracturing the top coal in front of the working face frame can directly fracture the top coal near the working face. However, since the top coal near the working face has been affected by mining and cracks have occurred, which affects the fracturing results, it is impossible to use the roof pressure to damage the top coal. Summary of the invention

[0005] The present invention provides a jet fracturing method for improving the coal caving rate of a fully mechanized caving working face of hard and thick top coal, so as to solve the defects in the prior art that the advanced drilling is easily affected by mining and the crack expansion is insufficient, so as to achieve more sufficient crack expansion.

[0006] The present invention provides a jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal, comprising: Construct the first directional long borehole into the top coal; Constructing a plurality of second directional long drill holes on the top plate, wherein the drilling direction of the second directional long drill holes is perpendicular to the working surface; Based on the plurality of the second directional long drill holes, the roof is subjected to jet fracturing so that the roof forms a rock block, and the rock block acts on the top coal; Based on the first directional long drill hole, the top coal is fractured.

[0007] According to a jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal provided by the present invention, the construction of a first directional long borehole toward the top coal comprises: A plurality of first directional long drill holes are constructed toward the top coal, and the drilling directions of the first directional long drill holes are perpendicular to the working face.

[0008] According to a jet fracturing method for improving the coal caving rate of a fully mechanized caving working face of hard and thick top coal provided by the present invention, a plurality of second directional long boreholes are constructed toward the roof, and the drilling direction of the second directional long boreholes is perpendicular to the working face, comprising: The plurality of the second directional long boreholes include at least one middle rock hole and two end rock holes, and the two end rock holes are respectively located on both sides of the middle rock hole.

[0009] According to a jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal provided by the present invention, the jet fracturing of the top plate based on the plurality of the second directional long drill holes so that the top plate forms a rock block, and the rock block acts on the top coal, comprising: The top plate is impacted by high-pressure water jets and abrasive particles to produce a cutting effect and form prefabricated cracks in a predetermined direction; Fracturing is performed based on the prefabricated fractures, and the hydraulic fractures will expand along the direction of the prefabricated fractures to achieve directional fracturing of the roof.

[0010] According to a jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal provided by the present invention, the jet fracturing of the top plate based on the plurality of the second directional long drill holes so that the top plate forms a rock block, and the rock block acts on the top coal, comprising: The end rock hole is subjected to directional jetting and post-fracturing in a direction perpendicular to the horizontal plane, so as to form a vertical crack on the top plate of the two end heads; The middle rock hole is subjected to directional jetting and post-fracture in the horizontal direction to form a horizontal crack, and the horizontal crack and the vertical crack are connected to form a rock block in the top plate.

[0011] According to a jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal provided by the present invention, the jet fracturing of the top plate based on the plurality of the second directional long drill holes so that the top plate forms a rock block, and the rock block acts on the top coal, further comprising: During the mining process at the working face, the pressing blocks can rotate from both ends to act on the top coal, thereby destroying the integrity of the top coal by means of the pressure of the roof.

[0012] According to a jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal provided by the present invention, the top coal is fractured based on the first directional long drilling hole, comprising: For the first directional long borehole, non-directional multi-cluster high-pressure water jets are used to impact the top coal, and non-directional channels are reserved in the first directional long borehole.

[0013] According to a jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal provided by the present invention, the top coal is fractured based on the first directional long drilling hole, comprising: A non-directional multi-cluster hydraulic jet device is used to inject complex cuts in the first directional long borehole with three nozzles evenly distributed at an angle of 120 degrees.

[0014] According to a jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal provided by the present invention, the top coal is fractured based on the first directional long drilling hole, comprising: A non-directional multi-cluster hydraulic jet device is used to inject multiple cuts in the first directional long borehole, and the angles between adjacent cuts are equal.

[0015] According to a jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal provided by the present invention, the first directional long borehole is constructed toward the top coal, comprising: A directional drilling rig is used to construct multiple first directional long boreholes into the top coal.

[0016] The jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal provided by the present invention comprises the following steps: constructing a first directional long borehole into the top coal; constructing a plurality of second directional long boreholes into the top plate, wherein the drilling directions of the second directional long boreholes are perpendicular to the working face; the advanced boreholes are not affected by mining, and the crack expansion is more sufficient; based on the plurality of second directional long boreholes, jet fracturing is performed on the top plate; so that a rock block is formed on the top plate, and the rock block acts on the top coal, which can reduce the pressure step distance, so that the rock is broken and rotated in time and acts on the coal body; based on the first directional long borehole, the top coal is fractured, which can increase the density and complexity of the hydraulic fractures in the coal holes. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a side view of the structural distribution of the first directional long drill hole and the second directional long drill hole provided by the present invention.

[0019] Figure 2 This is a front view of the structural distribution of the first directional long drill hole and the second directional long drill hole provided by the present invention.

[0020] Figure 3 It is a structural schematic diagram of the top plate drilling directional jet provided by the present invention.

[0021] Figure 4 It is a schematic diagram of the structure of the compressed blocks formed by top plate drilling and fracturing provided by the present invention.

[0022] Figure 5 This is one of the schematic diagrams of the rock block provided by the present invention acting on the coal body roof drilling jet fracturing effect.

[0023] Figure 6 This is the second schematic diagram of the effect of rock blocks provided by the present invention on the drilling jet fracturing of the coal roof.

[0024] Figure 7 It is a structural schematic diagram of the first directional long-hole non-directional multi-cluster jet provided by the present invention.

[0025] Figure 8 It is a schematic structural diagram of the first directional long-hole fracturing provided by the present invention.

[0026] Reference numerals: 1. Top coal; 2. First directional long drill hole; 3. Roof; 4. Second directional long drill hole; 5. Working face; 6. Rock block; 41. Middle rock hole; 42. End rock hole. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0029] Combine the following Figure 1-Figure 8 The jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal of the present invention comprises: S1. Construct the first directional long borehole toward the top coal 1.

[0030] One or more first directional long boreholes 2 can be constructed into the top coal 1 by a directional drilling machine, which can be understood as rock holes, for providing channels for subsequent fracturing operations on the top coal 1. The first directional long boreholes 2 can be understood as coal holes.

[0031] S2, constructing a plurality of second directional long drill holes 4 on the roof 3, wherein the drilling direction of the second directional long drill holes 4 is perpendicular to the working surface. The second directional long drill holes 4 can be understood as rock holes.

[0032] A plurality of second directional long boreholes 4 can be constructed on the roof 3 by a directional drilling machine to ensure that the second directional long boreholes 4 are perpendicular to the working surface, thereby providing a channel for subsequent jet fracturing operations on the roof 3 .

[0033] S3. Based on a plurality of second directional long drill holes 4, jet fracturing is performed on the roof 3 so that a rock block 6 is formed on the roof 3, and the rock block acts on the top coal 1.

[0034] Through the jet fracturing technology, the roof 3 is forced to form a specific rock block structure, which will act on the top coal 1 in the subsequent process, helping to improve the crushing effect of the top coal 1. Through advanced drilling and fracturing, cracks in the roof 3 and top coal 1 of the working face caused by mining can be avoided, ensuring that the hydraulic fracturing is fully extended in the top fracture layer.

[0035] S4. Based on the first directional long drill hole 2, the top coal 1 is fractured.

[0036] The fracturing technology is used to further break up the top coal 1 and improve the coal discharge rate.

[0037] The jet fracturing method provided by the present invention is used to improve the coal caving rate of the hard rear top coal fully-mechanized caving working face. A directional drilling rig is used to advance the working face to construct a long-distance drilling hole. The advanced drilling hole is not affected by the mining, and the crack expansion is more sufficient. The first directional long borehole 2 adopts non-directional multi-cluster jet fracturing, which can increase the density and complexity of the hydraulic fractures in the coal holes.

[0038] like Figure 2 As shown, in a feasible embodiment of the present invention, step S1 includes: Constructing multiple first directional long boreholes 2 in the top coal 1, and the drilling direction of the first directional long boreholes 2 is perpendicular to the working face 5, which can more effectively penetrate the top coal 1, ensure that the fracturing fluid can be evenly distributed inside the top coal 1, and help to form a more complex and extensive hydraulic fracture network, thereby improving the crushing effect of the top coal 1. In addition, the drilling direction perpendicular to the working face makes the drilling operation more efficient and accurate, which helps to reduce drilling time and cost and improve overall operation efficiency. Moreover, by optimizing the drilling direction and number, the top coal can be more effectively crushed, making it easier to release from the working face, which helps to improve the coal release rate of the fully mechanized caving working face, thereby increasing coal production.

[0039] like Figure 2 As shown, in a feasible embodiment provided by the present invention, step S2 includes: The plurality of second directional long boreholes 4 include at least one middle rock hole 41 and two end rock holes 42, and the two end rock holes 42 are respectively located on both sides of the middle rock hole 41, so as to form a wider and more uniform fracturing area. The synergistic effect of the middle rock hole 41 and the end rock holes 42 on both sides helps to form a more complex hydraulic fracture network in the roof 3, thereby improving the crushing effect of the roof 3.

[0040] In a feasible embodiment provided by the present invention, more specifically, step S3 includes: The top plate 3 is impacted by a high-pressure water jet and abrasive particles, producing a cutting effect and forming a prefabricated crack in a predetermined direction. The high-pressure water jet is a process in which water is pressurized to an extremely high pressure (such as 200-400Mpa) by a high-pressure pump and then ejected at an extremely high speed through a small-aperture nozzle. In this process, abrasive particles (such as garnet, corundum, etc.) are added to the water jet, and these abrasive particles impact the top plate 3 at an extremely high speed under the drive of the high-pressure water flow. The impact of the abrasive particles, the shearing effect of the water jet, and the micro-machining effect of the abrasive on the surface of the material together achieve the cutting of the top plate 3. Due to the impact of the high-pressure water jet and the abrasive particles, the target material can be accurately cut to form a prefabricated crack in a predetermined direction.

[0041] Based on the prefabricated fractures, hydraulic fractures will expand in the direction of the prefabricated fractures to achieve directional fracturing of the roof 3. Directional fracturing can ensure the uniform distribution of the fracturing fluid in the roof 3, forming a more complex and extensive hydraulic fracture network, thereby improving the crushing effect of the roof. By optimizing the fracturing mechanism, the roof can be more effectively crushed, making it easier to release from the working face, thereby increasing coal production.

[0042] like Figure 3 As shown, further, step S3 includes: the end rock hole 42 is subjected to directional jetting and post-fracture along a direction perpendicular to the horizontal plane to form a vertical crack in the top plate 3 at both ends; the middle rock hole 41 is subjected to directional jetting and post-fracture along a horizontal direction to form a horizontal crack, the horizontal crack and the vertical crack are connected to form a rock block 6 in the top plate 3, which can reduce the pressure step distance.

[0043] like Figure 4 , Figure 5 and Figure 6 As shown, step S3 also includes: during the mining process of the working face, the rock block 6 can rotate from both ends and act on the top coal 1, and the integrity of the top coal 1 is destroyed by the pressure of the roof 3, so that the rock block 6 is broken and rotated in time and acts on the coal body.

[0044] In a feasible embodiment of the present invention, step S4 includes: for the first directional long borehole 2, non-directional multi-cluster high-pressure water jets are used to impact the top coal, and non-directional channels are reserved in the first directional long borehole 2. These water jets are not along a single predetermined direction, but can form multi-directional impacts inside the borehole. Parameters such as pressure, flow rate and injection angle of the high-pressure water jet are carefully designed to ensure that the top coal 1 can be effectively impacted and crushed. While the high-pressure water jet impact is being carried out, some non-directional channels or cracks will naturally form inside the borehole. The existence of these channels or cracks provides a channel for the subsequent injection of fracturing fluid, which helps to further crush the top coal 1.

[0045] like Figure 7 and Figure 8 As shown, in a feasible embodiment of the present invention, step S4 includes: using a non-directional multi-cluster hydraulic jet device, with three nozzles evenly distributed at an angle of 120°, the high-pressure water flow passes through the nozzles at a high speed, and produces a strong impact and cutting effect on the top coal 1 around the borehole. Since the nozzles are distributed at an angle of 120°, the high-pressure water flow can form slits in three directions inside the borehole. With the continuous injection of the high-pressure water flow, the top coal 1 of the first directional long borehole 2 is gradually cut and broken, and complex slits are ejected in the first directional long borehole 2.

[0046] In a feasible embodiment of the present invention, step S4 includes: using a non-directional multi-cluster hydraulic jet device to inject multiple slits in the first directional long borehole 2, and these slits not only extend along the axial direction of the first directional long borehole 2, but also may form a complex network in the radial and oblique directions of the first directional long borehole 2. And the angles between adjacent slits are equal, which helps to form a uniform slit network. The setting of slits with equal angles can optimize the crushing effect of the top coal 1, reduce the residue of large pieces of top coal 1, improve the stability of the drilling hole, and ensure the safety of the mining process.

[0047] In a feasible embodiment of the present invention, step S1 includes using a directional drilling rig to construct a plurality of first directional long boreholes 2 to the top coal 1, and determining the specific position of the first directional long boreholes 2 according to the mining design and geological exploration results. During the construction process, the drilling speed, pressure, torque and other parameters of the drilling rig are strictly controlled to ensure the accuracy and depth of the drilling. By constructing a plurality of first directional long boreholes 2, the top coal 1 can be more effectively crushed and fractured, thereby improving the recovery rate and mining efficiency of the coal.

[0048] Therefore, the jet fracturing method provided by the present invention for improving the coal caving rate of the fully-mechanized caving working face of hard and thick top coal adopts a directional drilling rig to construct the first directional long borehole at the advance working face. The advance borehole is not affected by mining, and the crack expansion is more sufficient; the second directional long borehole adopts directional jet fracturing to cut off the roof 3 from both ends to form a rock block 6, which can reduce the pressure step distance, so that the rock block 6 can be broken and transmitted back in time to act on the coal body; the first directional long borehole performs non-directional multi-cluster jet fracturing, which can increase the density and complexity of the hydraulic fractures in the coal holes.

[0049] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0050] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "mode", "specific mode", or "some modes" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or mode are included in at least one embodiment or mode of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or mode. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or modes in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or modes described in this specification and the features of the different embodiments or modes, without contradiction.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal, characterized in that: include: Constructing a first directional long borehole (2) toward the top coal (1); Constructing a plurality of second directional long drill holes (4) on the top plate (3), wherein the drilling direction of the second directional long drill holes (4) is perpendicular to the working surface (5); Based on the plurality of the second directional long drill holes (4), the roof (3) is subjected to jet fracturing, so that the roof (3) forms a rock block (6), and the rock block (6) acts on the top coal (1); Based on the first directional long drill hole (2), the top coal (1) is fractured.

2. The jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal according to claim 1 is characterized in that: The construction of the first directional long drilling hole (2) towards the top coal (1) comprises: A plurality of first directional long drill holes (2) are constructed toward the top coal (1), and the drilling direction of the first directional long drill holes (2) is perpendicular to the working face (5).

3. The jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal according to claim 1 is characterized in that: The method comprises constructing a plurality of second directional long drill holes (4) on the top plate (3), wherein the drilling direction of the second directional long drill holes (4) is perpendicular to the working surface, and comprises: The plurality of second directional long drill holes (4) include at least one middle rock hole (41) and two end rock holes (42), and the two end rock holes (42) are respectively located on both sides of the middle rock hole (41).

4. The jet fracturing method for improving the coal caving rate of a fully mechanized caving working face of hard and thick top coal according to claim 1 is characterized in that: The method of jet fracturing the roof (3) based on the plurality of the second directional long drill holes (4) so ​​as to form a rock block (6) on the roof (3), wherein the rock block (6) acts on the top coal (1), comprises: The top plate (3) is impacted by a high-pressure water jet and abrasive particles to produce a cutting effect, thereby forming prefabricated cracks in a predetermined direction; Based on the prefabricated fractures, hydraulic fractures will expand in the direction of the prefabricated fractures, thereby achieving directional fracturing of the top plate (3).

5. The jet fracturing method for improving the coal caving rate of a fully mechanized caving working face of hard and thick top coal according to claim 3 is characterized in that: The method of jet fracturing the roof (3) based on the plurality of the second directional long drill holes (4) so ​​as to form a rock block on the roof (3), wherein the rock block (6) acts on the top coal (1), comprises: The end rock hole (42) is subjected to directional jetting and post-fracture in a direction perpendicular to the horizontal plane, thereby forming a vertical crack on the top plate (3) at both ends; The middle rock hole (41) is subjected to directional jetting and post-fracture in the horizontal direction to form a horizontal crack, and the horizontal crack and the vertical crack are connected to form a rock block (6) in the top plate (3).

6. The jet fracturing method for improving the coal caving rate of a fully mechanized caving working face of hard and thick top coal according to claim 5 is characterized in that: The method of jet fracturing the roof based on the plurality of the second directional long drill holes (4) so ​​as to form a rock block (6) on the roof (3), wherein the rock block (6) acts on the top coal (1), further comprises: During the mining process at the working face, the rock block (6) can rotate from both ends to act on the top coal (1), thereby destroying the integrity of the top coal (1) with the help of the pressure of the roof plate (3).

7. The jet fracturing method for improving the coal caving rate of a fully mechanized caving working face of hard and thick top coal according to claim 1 is characterized in that: The fracturing of the top coal (1) based on the first directional long drill hole (2) comprises: For the first directional long drill hole (2), non-directional multi-cluster high-pressure water jets are used to impact the top coal, and a non-directional channel is reserved in the first directional long drill hole (2).

8. The jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal according to claim 7 is characterized in that: The fracturing of the top coal based on the first directional long drill hole (2) comprises: A non-directional multi-cluster hydraulic jet device is used to produce complex cuts in the first directional long borehole (2) using three jets evenly distributed at an angle of 120°.

9. The jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal according to claim 7, wherein the fracturing of the top coal (1) based on the first directional long drill hole (2) comprises: A non-directional multi-cluster hydraulic jet device is used to inject a plurality of cuts in the first directional long borehole (2), and the angles between adjacent cuts are equal.

10. The jet fracturing method for improving the coal caving rate of a fully-mechanized caving working face of hard and thick top coal according to claim 1, wherein the first directional long borehole is constructed toward the top coal, comprising: A directional drilling rig is used to construct a plurality of the first directional long boreholes (2) in the top coal (1).

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