Directional drilling and carbon dioxide fracturing combined dirt band weakening method and coal mining method

Abstract

The invention discloses a directional drilling and carbon dioxide fracturing combined dirt band weakening method and a coal mining method. The method comprises the steps that occurrence parameters of a dirt band layer in a coal seam are obtained; determining arrangement parameters of a directional drill hole, a fracturing drill hole and a carbon dioxide fracturing device for fracturing weakening of the dirt band layer in the dirt band layer; according to the arrangement parameters of the directional drilling and the fracturing drilling, drilling construction of the directional drilling and the fracturing drilling is conducted; a carbon dioxide fracturing device is arranged in the fracturing drill hole, and an orifice of the fracturing drill hole is blocked; the carbon dioxide cracking device is started to crack and weaken the dirt band layer; evaluating the weakened dirt band layer to obtain weakening evaluation data; and based on the weakening evaluation data, optimizing arrangement parameters of the directional drill hole, the fracturing drill hole and the carbon dioxide fracturing device in the dirt band layer. According to the embodiment of the invention, directional drilling and carbon dioxide fracturing are organically combined, sufficient fracturing weakening of the hard dirt band is realized, and the negative influence of the hard dirt band on coal cutting of a coal cutter is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mining, and in particular relates to a directional drilling and carbon dioxide fracturing combined with a gangue weakening method and a coal mining method. Background Art

[0002] Hard interlayers in coal seams refer to the hard and difficult-to-cut rock or mineral layer in the coal seams. Interlayers are usually composed of hard rocks such as quartz sandstone, flint, limestone, etc., and their hardness is much higher than that of coal seams. Hard interlayers in coal seams have many negative effects on the cutting of coal mining machines, which not only reduces equipment performance and production efficiency, but also increases safety risks and production costs.

[0003] In the related technology, the hard interlayer of coal seam is generally treated by deep hole blasting and other methods. Although it can effectively break up the interlayer, its disadvantages are also very prominent. Blasting will produce strong vibration, shock waves and harmful gases, which will greatly affect the stability of the roadway and easily cause damage to machinery and personnel. Summary of the invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems: The inventors have realized that the hazards of gangue in coal seams are as follows: (1) Reduced mining speed: The hardness of gangue is high and it is difficult to cut, which leads to a decrease in the working efficiency of the coal mining machine and a slowdown in the mining speed, affecting the overall production progress. (2) Increased equipment wear: When the coal mining machine cuts the gangue, the cutter and mechanical parts bear a greater load, which increases wear, shortens the life of the equipment, and increases maintenance and replacement costs. (3) High-temperature spark risk: High-temperature sparks are easily generated when cutting the gangue, which may ignite gas or coal dust in the coal seam, causing fire or explosion, threatening the lives of miners and mine facilities. (4) Increased equipment failure rate: Gangue causes load fluctuations of the coal mining machine, increases the risk of equipment failure, affects production continuity, and even causes safety accidents.

[0005] The inventors also realized that blasting will produce strong vibrations and shock waves that may cause the surrounding rock to loosen or be damaged, increasing the risk of roof collapse and spalling. Vibration may also damage equipment such as coal mining machines and hydraulic supports, shortening the service life of the equipment, and may damage the tunnel support structure, increasing the difficulty and cost of tunnel maintenance. Toxic and harmful gases such as carbon monoxide and nitrogen oxides are produced during the blasting process, threatening the health of miners. Blasting operations themselves are highly dangerous, and improper operation may cause accidents. Blasting may produce flying rocks, causing damage to equipment and personnel. Blasting may cause gas or coal dust explosions, especially in high-gas mines, where the risk is higher.

[0006] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0007] To this end, an embodiment of the present invention proposes a method for weakening rock inclusions by combining directional drilling and carbon dioxide fracturing, which can improve the fracturing and weakening effect of rock inclusions and is safe and controllable.

[0008] An embodiment of the present invention further provides a coal mining method.

[0009] The method for weakening gangue by combining directional drilling and carbon dioxide fracturing according to an embodiment of the present invention comprises: Obtain the occurrence parameters of interbedded gangue layers in coal seams; According to the occurrence parameters of the interlayer, the arrangement parameters of the directional drill hole, the fracturing drill hole and the carbon dioxide fracturing device used for fracturing and weakening the interlayer are determined, wherein the radial dimension of the directional drill hole is not less than 300 mm to form a free surface in the interlayer, and the fracturing drill hole is arranged adjacent to the directional drill hole so that the directional drill hole adjacent to the fracturing drill hole is located within the effective fracturing range of the carbon dioxide fracturing device; According to the arrangement parameters of the directional drilling hole and the fracturing drilling hole, drilling construction of the directional drilling hole and the fracturing drilling hole is performed; Arranging a carbon dioxide fracturing device in the fracturing borehole and plugging the orifice of the fracturing borehole; Starting the carbon dioxide fracturing device to fracture and weaken the interlayer; Evaluating the weakened interlayer to obtain weakening evaluation data; Based on the weakening assessment data, the arrangement parameters of the directional drilling holes, fracturing drilling holes and carbon dioxide fracturing devices in the interlayer are optimized.

[0010] The directional drilling and carbon dioxide fracturing combined with the interlayer weakening method of the embodiment of the present invention can provide a free surface by arranging a large-diameter directional drill hole in the interlayer, and can strengthen the carbon dioxide fracturing and weakening effect of the interlayer during the fracturing and weakening of the interlayer by the carbon dioxide fracturing device. A plastic zone is easily formed around the large-diameter directional drill hole, and the rock mass undergoes plastic deformation, and microcracks and crushing are prone to occur. The free surface formed by the directional drilling leads to the redistribution of the surrounding stress, and stress concentration is prone to occur around the directional drilling hole, causing local crushing. This embodiment organically combines directional drilling and carbon dioxide fracturing to achieve sufficient fracturing and weakening of hard interlayers, and reduce the negative impact of hard interlayers on coal cutting by coal mining machines.

[0011] In some embodiments, the step of obtaining the occurrence parameters of the interlayer in the coal seam includes collecting coal mine production geological data, detecting the interlayer by geophysical exploration and drilling to obtain detection data, and combining the production geological data and the detection data to determine the occurrence parameters of the interlayer, wherein the occurrence parameters include at least the number of layers, thickness, hardness and extended distribution range of the interlayer.

[0012] In some embodiments, the interlayer has a first extension direction, a second extension direction and a thickness direction, the directional drill holes and the fracturing drill holes are drilled along the first extension direction, and a plurality of the directional drill holes and a plurality of the fracturing drill holes are spaced and alternately arranged in the second extension direction; Each of the fracturing boreholes is provided with directional drill holes adjacent to the fracturing borehole on both sides of the second extension direction, so that the fracturing borehole forms free surfaces on both sides of the second extension direction; The effective fracturing ranges of the carbon dioxide fracturing devices arranged in the plurality of fracturing boreholes overlap to cover the interlayer.

[0013] In some embodiments, when the thickness of the interlayer is less than or equal to 1000 mm, the radial dimension of the directional drill hole is 300 mm to 600 mm, and the directional drill hole is located in the middle of the thickness direction of the interlayer; When the thickness of the interlayer is greater than 1000 mm, the plurality of directional drill holes are arranged in groups in the thickness direction of the interlayer to form a directional hole group, the sum of the radial dimensions of the plurality of directional drill holes in the directional hole group is 30% to 60% of the thickness of the interlayer, the fracturing drill holes and the directional hole group are arranged at intervals in the second extension direction, and at least some of the directional drill holes in the directional hole group are located on both sides of the fracturing drill holes in the thickness direction.

[0014] In some embodiments, the length of the directional drilling hole is 80m to 150m; And / or, a branch drill hole is further provided in the interlayer, the branch drill hole is connected to the directional drill hole, the radial dimension of the branch drill hole is smaller than the radial dimension of the directional drill hole, the branch drill hole extends in a direction close to the adjacent fracturing drill hole, and the branch drill hole is not connected to the fracturing drill hole.

[0015] In some embodiments, the step of arranging a carbon dioxide fracturing device in the fracturing borehole includes placing a plurality of carbon dioxide fracturing devices in series in the fracturing borehole to form a chain fracturing device, and plugging the orifice of the fracturing borehole, wherein the plugging length of the fracturing borehole is greater than a first threshold value, so as to reduce the amount of gas leaked from the orifice of the fracturing borehole after the chain fracturing device is activated; In the step of starting the carbon dioxide fracturing device, the carbon dioxide fracturing devices in the plurality of fracturing boreholes are started simultaneously.

[0016] In some embodiments, the step of evaluating the weakened interlayer to obtain weakening evaluation data includes: Detecting the inner wall of the directional borehole based on an imaging device to obtain the degree of wall fragmentation and crack development of the directional borehole according to the imaging information; Based on the difference in dielectric constant of the rock mass detected by the borehole radar, the broken zones, cracks and cavities in the weakened interlayer are identified; The weakened interlayer is evaluated to obtain the degree of crushing of different sections in the interlayer.

[0017] In some embodiments, the step of optimizing the arrangement parameters of the directional drilling, fracturing drilling and carbon dioxide fracturing device in the interlayer based on the weakening assessment data comprises: The crushing degree of the interlayer is graded, and divided into an over-crushed section, a well-crushed section and a section with poorly developed fractures in descending order according to the crushing degree; Building a feature database based on the crushing degree of different sections in the interlayer, the occurrence parameters of the interlayer, the layout parameters of the directional drilling holes in different sections in the interlayer, the layout parameters of the fracturing drilling holes and the layout parameters of the carbon dioxide fracturing device; The arrangement parameters of the directional drilling holes, the arrangement parameters of the fracturing drilling holes and the arrangement parameters of the carbon dioxide fracturing device corresponding to the over-fragmented section and the underdeveloped fracture section are optimized to iteratively optimize the feature database.

[0018] The coal mining method according to the embodiment of the present invention comprises: S1. Determine whether the thickness of the interlayer of coal seam is greater than a second threshold and whether the hardness of the interlayer of coal seam is greater than a third threshold; S2. If yes, the interlayer of coal seam is weakened by using the combined directional drilling and carbon dioxide fracturing method as described in any of the above embodiments; S3. Use coal mining machines to carry out coal mining operations.

[0019] In some embodiments, the coal mining method further comprises: S4. When advancing to the next coal seam containing interbedded gangue layers, repeat steps S1 to S3, and determine the layout parameters of directional drilling holes in the interbedded gangue layers, the layout parameters of fracturing drilling holes, and the layout parameters of carbon dioxide fracturing devices based on the iteratively optimized feature database. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the arrangement of directional drilling and fracturing drilling in an embodiment of the present invention.

[0021] Figure 2 It is a flow chart of a method for weakening gangue combined with directional drilling and carbon dioxide fracturing according to an embodiment of the present invention.

[0022] Figure 3 It is a flow chart of the coal mining method according to an embodiment of the present invention.

[0023] Reference numerals: 1. Interlayer of gangue; 2. Directional drilling; 3. Fracture drilling; 4. Cracks. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0025] The following describes a method for weakening interlayer gangue and a method for coal mining using directional drilling and carbon dioxide fracturing in combination with an embodiment of the present invention.

[0026] like Figure 1-Figure 3 As shown, the method for weakening interlayer gangue combined with directional drilling and carbon dioxide fracturing according to an embodiment of the present invention comprises: S101. Obtain the occurrence parameters of the interlayer 1 in the coal seam. Specifically, the coal mine production geological data can be collected to obtain the geological structure, ore deposit geology, geological disasters, environmental geology and other data of the location. Of course, basic production geological data can also be obtained through field investigation, exploration, literature query or laboratory analysis and testing. The interlayer 1 can also be detected by geophysical exploration and drilling to obtain detection data. The occurrence parameters of the interlayer 1 are determined in combination with the production geological data and the detection data. The occurrence parameters include at least the number of layers, thickness, hardness and extended distribution range of the interlayer 1. It is understandable that in order to improve the safety and controllability during the construction process, the surrounding environment information of the interlayer 1 can also be comprehensively judged through the above-mentioned information to reduce the disturbance to the surrounding environment.

[0027] S102, according to the occurrence parameters of the interlayer 1, determine the arrangement parameters of the directional drill hole 2, the fracturing drill hole 3 and the carbon dioxide fracturing device used for fracturing and weakening the interlayer 1. Among them, the radial dimension of the directional drill hole 2 is not less than 300 mm to form a free surface in the interlayer 1. In this embodiment, the large-diameter directional drill hole 2 is used to form an effective free surface in the interlayer 1, and the stress distribution of the interlayer 1 in the surrounding area of ​​the directional drill hole 2 is changed, so that stress concentration is likely to occur around the directional drill hole 2, thereby causing local fracture. The fracturing drill hole 3 is arranged adjacent to some directional drill holes 2, so that the directional drill holes 2 adjacent to the fracturing drill hole 3 are located within the effective fracturing range of the carbon dioxide fracturing device.

[0028] The distance referred to by "adjacent" in this embodiment is the radius size of the effective fracturing range of the carbon dioxide fracturing device arranged in the fracturing borehole 3. In other words, the distance between the directional borehole 2 and the fracturing borehole 3 adjacent to each other is smaller than the radius size of the effective fracturing range of the carbon dioxide fracturing device arranged in the fracturing borehole 3, ensuring that the directional borehole 2 is located in the effective fracturing range of the carbon dioxide fracturing device. By arranging the free surface, the fracturing weakening effect of the carbon dioxide fracturing device on the interlayer 1 is enhanced.

[0029] It can be understood that the interlayer 1 is flat and extends in the circumferential direction. When the directional drilling hole 2 is not set, the interlayer 1 is easier to break in the thickness direction during the fracturing process, and more impact energy in the carbon dioxide fracturing device will diffuse into the coal seam along the thickness direction of the interlayer 1, resulting in poor fracturing and weakening effect of the interlayer 1. Compared with not setting the directional drilling hole 2, the arrangement of the large-diameter directional drilling hole 2 in this embodiment can make the interlayer 1 easier to break around the directional drilling hole 2, so that more impact energy generated by the carbon dioxide fracturing device diffuses in the direction toward the free surface, thereby improving the fracturing and weakening effect of the interlayer 1. At the same time, this embodiment can also reduce the filling amount of the carbon dioxide fracturing device.

[0030] S103 , performing drilling construction of the directional drilling hole 2 and the fracturing drilling hole 3 according to the arrangement parameters of the directional drilling hole 2 and the fracturing drilling hole 3 .

[0031] When constructing the directional drilling hole 2 and the fracturing drilling hole 3, a directional drilling machine and a mining rotary directional drilling system can be used to drill in the hard interlayer 1. The aperture of the directional drilling hole 2 is not less than 300 mm to ensure that it can form a free surface of effective size. The aperture size of the fracturing drilling hole 3 is determined according to the size of the carbon dioxide fracturing device to ensure that the outer wall surface of the carbon dioxide fracturing device is in close contact with the inner wall surface of the fracturing drilling hole 3 after the carbon dioxide fracturing device is transported into the fracturing drilling hole 3.

[0032] The directional drill holes 2 and the fracturing drill holes 3 can be arranged at intervals and staggered. It can be understood that at least one directional drill hole 2 is arranged on the opposite sides of each fracturing drill hole 3, so that when the interlayer 1 is fractured and weakened, more impact energy can be diffused along the extension direction of the interlayer 1, thereby improving the crushing effect of the interlayer 1.

[0033] S104, a carbon dioxide fracturing device is arranged in the fracturing borehole 3, and the opening of the fracturing borehole 3 is blocked to prevent gas leakage from the opening of the fracturing borehole 3 during the fracturing process, thereby improving the fracturing weakening effect on the interlayer 1.

[0034] S105, start the carbon dioxide fracturing device to fracture and weaken the interlayer 1, so as to generate cracks 4 in the interlayer 1 to achieve crushing. When multiple fracturing boreholes 3 are arranged in the interlayer 1, the carbon dioxide fracturing devices in the multiple fracturing boreholes 3 can be started simultaneously or one by one.

[0035] S106, evaluating the weakened interlayer 1 to obtain weakening evaluation data. The weakening evaluation data can reflect the crack development and breakage of the interlayer 1.

[0036] S107, based on the weakening assessment data, optimize the layout parameters of the directional drill hole 2, the fracturing drill hole 3 and the carbon dioxide fracturing device in the interlayer 1. It can be understood that after the previous fracturing and weakening, by analyzing the weakening assessment data after the fracturing and weakening of the interlayer 1, the iterative optimization of the layout parameters in step S102 can be performed, which can help improve the subsequent fracturing and weakening effect of the interlayer 1.

[0037] The directional drilling and carbon dioxide fracturing combined with the interlayer weakening method of the embodiment of the present invention can provide a free surface by arranging a large-diameter directional drilling hole 2 in the interlayer 1. The carbon dioxide fracturing and weakening effect can be enhanced during the fracturing and weakening process of the interlayer 1 by the carbon dioxide fracturing device. A plastic zone is easily formed around the large-diameter directional drilling hole 2, and the rock mass undergoes plastic deformation, and microcracks and crushing are prone to occur. The free surface formed by the directional drilling hole 2 causes the surrounding stress to be redistributed, and stress concentration is prone to occur around the directional drilling hole 2, causing local crushing. This embodiment organically combines the directional drilling hole 2 and carbon dioxide fracturing to achieve sufficient fracturing and weakening of hard interlayers, and reduce the negative impact of hard interlayers on coal cutting by coal mining machines.

[0038] In this embodiment, carbon dioxide exists in liquid state when the pressure is greater than 7.35MPa and lower than 31°C, and begins to vaporize when the temperature exceeds this value, and the pressure changes continuously with the temperature to reach a supercritical state. Utilizing this property, liquid carbon dioxide is filled in the main pipe of the fracturing device, and the liquid carbon dioxide is quickly excited by the detonator. Within 40ms, the liquid carbon dioxide in the main pipe is rapidly vaporized, and the volume expands by about 600 times in an instant, producing a large amount of high-pressure carbon dioxide gas, and generating stress waves to impact the target rock mass, thereby achieving the purpose of fracturing the rock mass. Liquid carbon dioxide phase change fracturing belongs to the physical blasting fracturing process. Compared with the traditional rock blasting method, the carbon dioxide phase change fracturing process is more controllable and safer.

[0039] In the intact dense rock mass, the absence of free surfaces will result in a limited range of fracture weakening in the interlayer, making it difficult to fully fracture a large range of interlayers. The stress waves generated during the gasification of carbon dioxide will be reflected at the free surface as tensile waves, which help to break the interlayers. The presence of free surfaces makes this reflection more effective, thereby improving the efficiency and effect of fracture weakening. The presence of free surfaces reduces the resistance of interlayers to the pressure generated during the gasification process, that is, the clamping effect, which reduces the difficulty of breaking the interlayers and reduces the amount of carbon dioxide filled per unit.

[0040] The following describes some other specific embodiments of the method for weakening gangue combined with directional drilling and carbon dioxide fracturing according to the present invention.

[0041] like Figures 1 to 3 As shown, the combined directional drilling and carbon dioxide fracturing method for weakening interlayer gangue includes: S101. Obtain the occurrence parameters of the interlayer 1 in the coal seam. Specifically, the coal mine production geological data can be collected to obtain the geological structure, ore deposit geology, geological disasters, environmental geology and other data of the location. Of course, basic production geological data can also be obtained through field investigation, exploration, literature query or laboratory analysis and testing. The interlayer 1 can also be detected by geophysical exploration and drilling to obtain detection data. The occurrence parameters of the interlayer 1 are determined in combination with the production geological data and the detection data. The occurrence parameters include at least the number of layers, thickness, hardness and extended distribution range of the interlayer 1. It is understandable that in order to improve the safety and controllability during the construction process, the surrounding environment information of the interlayer 1 can also be comprehensively judged through the above-mentioned information to reduce the disturbance to the surrounding environment.

[0042] S102, according to the occurrence parameters of the interlayer 1, determine the arrangement parameters of the directional drill hole 2, the fracturing drill hole 3 and the carbon dioxide fracturing device used for fracturing and weakening the interlayer 1. It can be understood that the interlayer 1 has a first extension direction, a second extension direction and a thickness direction, and the directional drill hole 2 and the fracturing drill hole 3 are drilled along the first extension direction, and multiple directional drill holes 2 and multiple fracturing drill holes 3 are arranged alternately and at intervals in the second extension direction. Each fracturing drill hole 3 is arranged with directional drill holes 2 adjacent to the fracturing drill hole 3 on both sides of the second extension direction, so that the fracturing drill hole 3 forms free surfaces on both sides of the second extension direction. The effective fracturing ranges of the carbon dioxide fracturing devices arranged in the multiple fracturing drill holes 3 overlap to cover the interlayer 1.

[0043] The first extension direction may extend generally along the front-back direction in the figure, for example, the first extension direction may generally be approximately the same as the direction of coal seam mining. For another example, when the stratum inclination of the interlayer is at a certain angle to the excavation direction of the coal seam, in order to ensure that the directional drilling hole is in the interlayer, at this time, the first extension direction is at a certain angle to the mining direction of the coal seam. The second extension direction may extend generally along the left-right direction in the figure, for example, the second extension direction may generally extend along the radial direction of the mining face, and the thickness direction may extend generally along the up-down direction in the figure.

[0044] It can be understood that the first extension direction and the second extension direction are both substantially perpendicular to the thickness direction. When the interlayer to be fractured and weakened is a relatively regular cuboid, the first extension direction, the second extension direction and the thickness direction may be orthogonal to each other.

[0045] In this embodiment, the radial dimension of the directional drill hole 2 is not less than 300 mm to form an effective free surface in the interlayer 1 .

[0046] Preferably, when the thickness of the interlayer 1 is less than or equal to 1000mm, the radial dimension of the directional drill hole 2 is 300mm to 600mm, and the directional drill hole 2 is located in the middle of the thickness direction of the interlayer 1. It is understandable that the directional drill hole 2 is usually selected in the interlayer 1 with a thickness greater than 300mm. When the thickness of the interlayer 1 in a large range in the second extension direction is less than 300mm, or when the thickness of the interlayer 1 in the first extension direction changes and is less than 300mm, in order to improve the fracture weakening effect of the interlayer 1, at this time, a part of the large-diameter directional drill holes set on the interlayer 1 will be located in the coal seams on both sides of the thickness direction of the interlayer 1.

[0047] When the thickness of the interlayer 1 is greater than 1000 mm, a plurality of directional drill holes 2 are arranged in groups in the thickness direction of the interlayer 1 to form a directional hole group. The sum of the radial dimensions of the plurality of directional drill holes 2 in the directional hole group is 30% to 60% of the thickness of the interlayer 1, and the fracturing drill holes 3 and the directional hole group are arranged at intervals in the second extension direction. At least part of the directional drill holes 2 in the directional hole group are located on both sides of the fracturing drill holes 3 in the thickness direction. In other words, the plurality of directional drill holes 2 in the directional hole group can be arranged roughly symmetrically in the thickness direction, thereby ensuring that an effective free surface with sufficient size and area is formed in the interlayer 1.

[0048] For example, when the thickness of the interlayer 1 is 1200 mm, the radial dimension of the directional drill hole 2 can be 350 mm. The number of directional drill holes 2 in each directional hole group is two, one of which is arranged above the fracturing drill hole 3 in the thickness direction, and the other directional drill hole 2 is arranged below the fracturing drill hole 3 in the thickness direction.

[0049] For another example, when the thickness of the interlayer 1 is 2000 mm, the radial dimension of the directional drill hole 2 can be 300 mm. The number of directional drill holes 2 in each directional hole group is three. At this time, one directional drill hole 2 is arranged in the middle of the thickness direction of the interlayer 1, the second directional drill hole 2 is arranged above the fracturing drill hole 3 in the thickness direction, and the third directional drill hole 2 is arranged below the fracturing drill hole 3 in the thickness direction.

[0050] It is understandable that when the thickness of the interlayer 1 in the coal seam is relatively thin, the performance of the coal mining machine is less affected, and no fracturing and weakening is required. When the thickness of the interlayer 1 in the coal seam is too thick, the coal seam may be divided into multiple independent coal seams for mining. Preferably, the thickness of the interlayer 1 applicable to the directional drilling and carbon dioxide fracturing combined with interlayer weakening method of this embodiment is 300mm to 2000mm.

[0051] Furthermore, a branch borehole is provided in the interlayer 1, the branch borehole is connected with the directional borehole 2, the radial dimension of the branch borehole is smaller than the radial dimension of the directional borehole 2, the branch borehole extends toward the direction close to the adjacent fracturing borehole 3, and the branch borehole is not connected with the fracturing borehole 3. When the thickness of a local section of the interlayer 1 suddenly thickens, the branch borehole can be drilled on the side wall of the directional borehole 2, and the branch borehole can be used to increase the free surface size of the corresponding section and improve the fracturing weakening effect of the corresponding section.

[0052] The length of the directional borehole 2 in the first extension direction is 80m to 150m. On the one hand, the length of the directional borehole 2 can be determined according to the space size of the tunnel and the performance of the underground equipment. On the other hand, it can be determined according to the progress of each layer of excavation and mining, and the interlayer 1 can be weakened section by section to improve work efficiency. For example, the length of the directional borehole 2 in the first extension direction is 80m, 95m, 100m, 120m or 150m. When the length of the directional borehole 2 in the first extension direction is less than 80m, it is easy to cause frequent interlayer weakening construction, affecting the construction efficiency. When the length of the directional borehole 2 in the first extension direction is greater than 150m, the performance requirements of the underground equipment are high, and it is difficult to obtain the occurrence parameters of the interlayer 1, resulting in problems such as difficulty in construction of large-diameter directional boreholes 2 and poor interlayer weakening effect.

[0053] In this embodiment, the use of a large-diameter directional drill hole 2 can form an effective free surface in the interlayer 1, change the stress distribution of the interlayer 1 in the area around the directional drill hole 2, and make it easy for stress concentration to occur around the directional drill hole 2, thereby causing local fracture. The fracturing drill hole 3 is arranged adjacent to some of the directional drill holes 2, so that the directional drill holes 2 adjacent to the fracturing drill hole 3 are located within the effective fracturing range of the carbon dioxide fracturing device.

[0054] The distance referred to by "adjacent" in this embodiment is the radius size of the effective fracturing range of the carbon dioxide fracturing device arranged in the fracturing borehole 3. In other words, the distance between the directional borehole 2 and the fracturing borehole 3 adjacent to each other is smaller than the radius size of the effective fracturing range of the carbon dioxide fracturing device arranged in the fracturing borehole 3, ensuring that the directional borehole 2 is located in the effective fracturing range of the carbon dioxide fracturing device. By arranging the free surface, the fracturing weakening effect of the carbon dioxide fracturing device on the interlayer 1 is enhanced.

[0055] It can be understood that the interlayer 1 is flat and extends in the circumferential direction. When the directional drilling hole 2 is not set, the interlayer 1 is easier to break in the thickness direction during the fracturing process, and more impact energy in the carbon dioxide fracturing device will diffuse into the coal seam along the thickness direction of the interlayer 1, resulting in poor fracturing and weakening effect of the interlayer 1. Compared with not setting the directional drilling hole 2, the arrangement of the large-diameter directional drilling hole 2 in this embodiment can make the interlayer 1 easier to break around the directional drilling hole 2, so that more impact energy generated by the carbon dioxide fracturing device diffuses in the direction toward the free surface, thereby improving the fracturing and weakening effect of the interlayer 1. At the same time, this embodiment can also reduce the filling amount of the carbon dioxide fracturing device.

[0056] S103 , performing drilling construction of the directional drilling hole 2 and the fracturing drilling hole 3 according to the arrangement parameters of the directional drilling hole 2 and the fracturing drilling hole 3 .

[0057] When constructing the directional drilling hole 2 and the fracturing drilling hole 3, a directional drilling machine and a mining rotary directional drilling system can be used to drill in the hard interlayer 1. The aperture of the directional drilling hole 2 is not less than 300 mm to ensure that it can form a free surface of effective size, and the aperture size of the fracturing drilling hole 3 is determined according to the size of the carbon dioxide fracturing device to ensure that the outer wall surface of the carbon dioxide fracturing device is in close contact with the inner wall surface of the fracturing drilling hole 3 after the carbon dioxide fracturing device is transported into the fracturing drilling hole 3.

[0058] S104, a carbon dioxide fracturing device is arranged in the fracturing borehole 3, and the opening of the fracturing borehole 3 is blocked to prevent gas leakage from the opening of the fracturing borehole 3 during the fracturing process, thereby improving the fracturing weakening effect on the interlayer 1.

[0059] Specifically, a plurality of carbon dioxide fracturing devices may be connected in series and placed in the fracturing borehole 3 to form a chain fracturing device, and then the orifice of the fracturing borehole 3 is blocked, and the blocking length of the fracturing borehole 3 is greater than a first threshold value to reduce the amount of gas leaking from the orifice of the fracturing borehole 3 after the chain fracturing device is activated.

[0060] The first threshold value can be set according to the energy level after the fracturing device is activated, and after the fracturing device is activated, the gas leakage at the orifice of the fracturing borehole 3 is reduced. For example, the first threshold value can be set to 1m to 2.5m.

[0061] S105, starting the carbon dioxide fracturing device to fracture and weaken the interlayer 1. When a plurality of fracturing boreholes 3 are arranged in the interlayer 1, the carbon dioxide fracturing devices in the plurality of fracturing boreholes 3 can be started simultaneously or one by one.

[0062] S106, evaluating the weakened interlayer 1 to obtain weakening evaluation data. The weakening evaluation data can reflect the crack development and breakage of the interlayer 1.

[0063] Specifically, the inner wall of the directional borehole 2 can be detected based on the imaging equipment to obtain the degree of wall fragmentation and the development of fractures in the directional borehole 2 according to the imaging information.

[0064] Based on the dielectric constant difference of the rock mass detected by borehole radar, the broken zones, cracks and cavities in the weakened interlayer 1 are identified.

[0065] The weakened interlayer 1 is evaluated to obtain the crushing degree of different sections in the interlayer 1. And combined with the performance of the coal mining machine, it is judged whether the weakened interlayer 1 is within the load bearing range of the mechanical parts.

[0066] S107, based on the weakening assessment data, optimize the layout parameters of the directional drill hole 2, the fracturing drill hole 3 and the carbon dioxide fracturing device in the interlayer 1. It can be understood that after the previous fracturing and weakening, by analyzing the weakening assessment data after the fracturing and weakening of the interlayer 1, the iterative optimization of the layout parameters in step S102 can be performed, which can help improve the subsequent fracturing and weakening effect of the interlayer 1.

[0067] Specifically, the crushing degree of the interlayer 1 can be graded, and divided into an over-crushed section, a well-crushed section, and a section with underdeveloped fissures according to the crushing degree from high to low. Among them, the over-crushed section may refer to the section where the interlayer 1 is much lower than the maximum load that the mechanical parts of the coal mining machine can withstand after being weakened. The well-crushed section may refer to the section where the interlayer 1 is within the effective load range that the mechanical parts of the coal mining machine can withstand after being weakened, which can ensure the normal and stable operation of the coal mining machine. The section with underdeveloped fissures may refer to the section where the interlayer 1 has incompletely developed fissures, and the coal mining machine will still bear a large load during excavation.

[0068] The over-crushed sections and well-crushed sections of the interlayer 1 both indicate that the crushing and weakening effect of the interlayer 1 is good. However, the over-crushed section indicates that there may be factors such as the close distance between the directional drilling hole 2 and the fracturing drilling hole 3 and the excessive filling amount of the carbon dioxide fracturing device. Parameters such as drilling and filling amount can be optimized to reduce construction costs.

[0069] The underdeveloped fracture sections indicate that there may be factors such as the distance between directional drilling hole 2 and fracturing drilling hole 3 is too far, the free surface formed by directional drilling hole 2 is too small, and the filling amount of the carbon dioxide fracturing device is too small. Therefore, parameters such as drilling and filling amount can be optimized for the corresponding sections to improve the fracturing weakening effect.

[0070] A feature database is constructed based on the crushing degree of different sections in the interlayer 1, the occurrence parameters of the interlayer 1, the layout parameters of the directional drilling holes 2 in different sections of the interlayer 1, the layout parameters of the fracturing drilling holes 3 and the layout parameters of the carbon dioxide fracturing device. The feature database can establish matching layout parameters for the interlayer 1 with different occurrence parameters to guide the subsequent interlayer weakening process.

[0071] The layout parameters of the directional drilling hole 2, the layout parameters of the fracturing drilling hole 3 and the layout parameters of the carbon dioxide fracturing device corresponding to the over-fragmented section and the underdeveloped fracture section are optimized to iteratively optimize the feature database. This embodiment can optimize the parameters of the drilling hole, the filling amount parameters of the carbon dioxide fracturing device, etc. through iterative optimization of the feature database, thereby reducing the construction cost and improving the work efficiency and the fracturing weakening effect.

[0072] The directional drilling and carbon dioxide fracturing combined with the interlayer weakening method of the embodiment of the present invention can provide a free surface by arranging a large-diameter directional drilling hole 2 in the interlayer 1. The carbon dioxide fracturing effect can be strengthened during the fracturing and weakening process of the interlayer 1 by the carbon dioxide fracturing device. A plastic zone is easily formed around the large-diameter directional drilling hole 2, and the rock mass undergoes plastic deformation, and microcracks and crushing are prone to occur. The free surface formed by the directional drilling hole 2 causes the surrounding stress to be redistributed, and stress concentration is prone to occur around the directional drilling hole 2, causing local crushing. This embodiment organically combines the directional drilling hole 2 and carbon dioxide fracturing to achieve sufficient fracturing and weakening of hard interlayers, and reduce the negative impact of hard interlayers on coal cutting by coal mining machines. In addition, the arrangement parameters of the directional drilling hole 2, the fracturing drilling hole 3, and the carbon dioxide fracturing device used for fracturing and weakening the interlayer 1 can be iteratively optimized to improve the subsequent operation efficiency and effect.

[0073] The coal mining method according to the embodiment of the present invention comprises: S1. Determine whether the thickness of the interlayer 1 in the coal seam is greater than a second threshold and whether the hardness of the interlayer 1 is greater than a third threshold.

[0074] Preferably, the second threshold value can be 250mm to 350mm. In other words, when the hardness of the interlayer 1 meets the third threshold value and the thickness of at least part of the section is greater than 250mm, or 260mm, or 300mm, or 350mm, the interlayer weakening method of directional drilling and carbon dioxide fracturing combined with the embodiment of the present invention can be used to carry out interlayer weakening treatment.

[0075] Preferably, the third threshold value may be that the Puerto Rico hardness coefficient of the gangue is greater than 4 to 7. In other words, when the thickness of the gangue layer 1 is greater than the second threshold value and the Puerto Rico hardness coefficient of the gangue in at least part of the section is greater than 4, 4.5, 6 or 7, the gangue weakening method combined with directional drilling and carbon dioxide fracturing according to the embodiment of the present invention can be used to perform gangue weakening treatment.

[0076] S2. If yes, adopt the combined directional drilling and carbon dioxide fracturing method as in any of the above embodiments to weaken the interlayer 1 in the coal seam. The weakening treatment of the interlayer 1 in this embodiment is the same as the steps and effects in the above embodiments, so it will not be repeated.

[0077] S3. Use coal mining machines to carry out coal mining operations.

[0078] S4. When advancing to the next coal seam containing the interlayer 1, repeat steps S1 to S3, and determine the layout parameters of the directional drill hole 2 in the interlayer 1, the layout parameters of the fracturing drill hole 3 and the layout parameters of the carbon dioxide fracturing device based on the iteratively optimized feature database.

[0079] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0080] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0081] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0082] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0083] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for weakening interlayer gangue by combining directional drilling and carbon dioxide fracturing, characterized in that: include: Obtain the occurrence parameters of interbedded gangue layers in coal seams; According to the occurrence parameters of the interlayer, the arrangement parameters of the directional drill hole, the fracturing drill hole and the carbon dioxide fracturing device used for fracturing and weakening the interlayer are determined, wherein the radial dimension of the directional drill hole is not less than 300 mm to form a free surface in the interlayer, and the fracturing drill hole is arranged adjacent to the directional drill hole so that the directional drill hole adjacent to the fracturing drill hole is located within the effective fracturing range of the carbon dioxide fracturing device; According to the arrangement parameters of the directional drilling hole and the fracturing drilling hole, drilling construction of the directional drilling hole and the fracturing drilling hole is performed; Arranging a carbon dioxide fracturing device in the fracturing borehole and plugging the orifice of the fracturing borehole; Starting the carbon dioxide fracturing device to fracture and weaken the interlayer; Evaluating the weakened interlayer to obtain weakening evaluation data; Based on the weakening assessment data, the arrangement parameters of the directional drilling holes, fracturing drilling holes and carbon dioxide fracturing devices in the interlayer are optimized.

2. The method for weakening interlayer gangue by combining directional drilling and carbon dioxide fracturing according to claim 1, characterized in that: The step of obtaining the occurrence parameters of the interlayer in the coal seam includes collecting coal mine production geological data, detecting the interlayer by geophysical exploration and drilling to obtain detection data, and combining the production geological data and the detection data to determine the occurrence parameters of the interlayer, wherein the occurrence parameters include at least the number of layers, thickness, hardness and extended distribution range of the interlayer.

3. The method for weakening interlayer gangue by combining directional drilling and carbon dioxide fracturing according to claim 1, characterized in that: The interlayer has a first extension direction, a second extension direction and a thickness direction, the directional drill holes and the fracturing drill holes are drilled along the first extension direction, and a plurality of the directional drill holes and the plurality of the fracturing drill holes are arranged alternately and at intervals in the second extension direction; Each of the fracturing boreholes is provided with directional drill holes adjacent to the fracturing borehole on both sides of the second extension direction, so that the fracturing borehole forms free surfaces on both sides of the second extension direction; The effective fracturing ranges of the carbon dioxide fracturing devices arranged in the plurality of fracturing boreholes overlap to cover the interlayer.

4. The method for weakening interlayer gangue by combining directional drilling and carbon dioxide fracturing according to claim 3 is characterized in that: When the thickness of the interlayer is less than or equal to 1000 mm, the radial dimension of the directional drill hole is 300 mm to 600 mm, and the directional drill hole is located in the middle of the thickness direction of the interlayer; When the thickness of the interlayer is greater than 1000 mm, the plurality of directional drill holes are arranged in groups in the thickness direction of the interlayer to form a directional hole group, the sum of the radial dimensions of the plurality of directional drill holes in the directional hole group is 30% to 60% of the thickness of the interlayer, the fracturing drill holes and the directional hole group are arranged at intervals in the second extension direction, and at least some of the directional drill holes in the directional hole group are located on both sides of the fracturing drill holes in the thickness direction.

5. The method for weakening interlayer gangue by combining directional drilling and carbon dioxide fracturing according to claim 3, characterized in that: The length of the directional drilling hole is 80m to 150m; And / or, a branch drill hole is further provided in the interlayer, the branch drill hole is connected to the directional drill hole, the radial dimension of the branch drill hole is smaller than the radial dimension of the directional drill hole, the branch drill hole extends in a direction close to the adjacent fracturing drill hole, and the branch drill hole is not connected to the fracturing drill hole.

6. The method for weakening interlayer gangue by combining directional drilling and carbon dioxide fracturing according to claim 1, characterized in that: The step of arranging a carbon dioxide fracturing device in the fracturing borehole includes connecting a plurality of carbon dioxide fracturing devices in series and placing them in the fracturing borehole to form a chain fracturing device, and plugging the orifice of the fracturing borehole. The plugging length of the fracturing borehole is greater than a first threshold value, so as to reduce the amount of gas leaked from the orifice of the fracturing borehole after the chain fracturing device is activated; In the step of starting the carbon dioxide fracturing device, the carbon dioxide fracturing devices in the plurality of fracturing boreholes are started simultaneously.

7. The method for weakening interlayer gangue by combining directional drilling and carbon dioxide fracturing according to claim 1, characterized in that: The step of evaluating the weakened interlayer to obtain weakening evaluation data comprises: Detecting the inner wall of the directional borehole based on an imaging device to obtain the degree of wall fragmentation and crack development of the directional borehole according to the imaging information; Based on the difference in dielectric constant of the rock mass detected by the borehole radar, the broken zones, cracks and cavities in the weakened interlayer are identified; The weakened interlayer is evaluated to obtain the degree of crushing of different sections in the interlayer.

8. The method for weakening interlayer gangue by combining directional drilling and carbon dioxide fracturing according to claim 7, characterized in that: The step of optimizing the arrangement parameters of the directional drilling holes, fracturing drilling holes and carbon dioxide fracturing devices in the interlayer based on the weakening assessment data includes: The crushing degree of the interlayer is graded, and is divided into an over-crushed section, a well-crushed section and a section with poorly developed fractures in descending order according to the crushing degree; Building a feature database based on the crushing degree of different sections in the interlayer, the occurrence parameters of the interlayer, the layout parameters of the directional drilling holes in different sections in the interlayer, the layout parameters of the fracturing drilling holes and the layout parameters of the carbon dioxide fracturing device; The arrangement parameters of the directional drilling holes, the arrangement parameters of the fracturing drilling holes and the arrangement parameters of the carbon dioxide fracturing device corresponding to the over-fragmented section and the underdeveloped fracture section are optimized to iteratively optimize the feature database.

9. A coal mining method, characterized in that: include: S1. Determine whether the thickness of the interlayer of coal seam is greater than a second threshold and whether the hardness of the interlayer of coal seam is greater than a third threshold; S2. If yes, the interlayer of coal seam is weakened by using the combined method of directional drilling and carbon dioxide fracturing as claimed in any one of claims 1 to 8; S3. Use coal mining machines to carry out coal mining operations.

10. The coal mining method according to claim 9, characterized in that: Also includes: S4. When advancing to the next coal seam containing interbedded gangue layers, repeat steps S1 to S3, and determine the layout parameters of directional drilling holes in the interbedded gangue layers, the layout parameters of fracturing drilling holes, and the layout parameters of carbon dioxide fracturing devices based on the iteratively optimized feature database.

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