Directional drilling and carbon dioxide fracturing combined with gangue weakening method and coal mining method

Abstract

The present invention discloses a combined directional drilling and carbon dioxide fracturing method for weakening interbedded gangue and a coal mining method. The method comprises obtaining the occurrence parameters of an interbedded gangue layer in a coal seam; determining the layout parameters of a directional drill hole, a fracturing drill hole, and a carbon dioxide fracturing device used to fracture and weaken the interbedded gangue layer in the interbedded gangue layer; drilling the directional drill hole and the fracturing drill hole according to the layout parameters of the directional drill hole and the fracturing drill hole; placing the carbon dioxide fracturing device in the fracturing drill hole and sealing the orifice of the fracturing drill hole; activating the carbon dioxide fracturing device to fracture and weaken the interbedded gangue layer; evaluating the weakened interbedded gangue layer to obtain weakening assessment data; and optimizing the layout parameters of the directional drill hole, the fracturing drill hole, and the carbon dioxide fracturing device in the interbedded gangue layer based on the weakening assessment data. The embodiments of the present invention organically combine directional drilling and carbon dioxide fracturing to achieve sufficient fracture and weakening of hard interbedded gangue, thereby reducing the negative impact of hard interbedded gangue on coal cutting by a coal mining machine.

Description

Technical Field

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

[0002] Hard interlayers in coal seams are layers of rock or minerals that are difficult to cut and are often found within the coal seam. These interlayers are typically composed of hard rocks such as quartz sandstone, flint, and limestone, and are much harder than the coal seam itself. These interlayers negatively impact shearer cutting, reducing equipment performance and production efficiency while also increasing safety risks and production costs.

[0003] Deep-hole blasting is commonly used to treat hard coal interlayers in coal seams. While this method effectively breaks up the interlayers, it also has significant drawbacks. Blasting generates strong vibrations, shock waves, and harmful gases, significantly impacting the stability of the roadway and potentially causing damage to equipment 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:

[0005] The inventors have recognized that the hazards of gangue in coal seams are as follows: (1) Reduced mining face advancement speed: Gangue is hard and difficult to cut, resulting in reduced working efficiency of the coal mining machine, slower mining face advancement speed, and affecting the overall production progress. (2) Increased equipment wear: When the coal mining machine cuts the gangue, the cutter and mechanical parts bear greater loads, aggravated wear, shortened equipment life, and increased maintenance and replacement costs. (3) Risk of high-temperature sparks: When cutting the gangue, high-temperature sparks are easily generated, 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 fluctuations in the load of the coal mining machine, increases the risk of equipment failure, affects production continuity, and even causes safety accidents.

[0006] 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.

[0007] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0008] To this end, an embodiment of the present invention proposes a gangue weakening method combining directional drilling and carbon dioxide fracturing, which can improve the fracturing and weakening effect of gangue and is safe and controllable.

[0009] An embodiment of the present invention further provides a coal mining method.

[0010] The method for weakening interbedded gangue by combining directional drilling and carbon dioxide fracturing according to an embodiment of the present invention comprises:

[0011] Obtain the occurrence parameters of interbedded gangue layers in coal seams;

[0012] Determining, based on the occurrence parameters of the interbedded gangue layer, the arrangement parameters of the directional drill hole, the fracturing drill hole, and the carbon dioxide fracturing device used to fracture and weaken the interbedded gangue layer in the interbedded gangue layer, wherein the radial dimension of the directional drill hole is not less than 300 mm to form a free surface in the interbedded gangue layer, 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 within the effective fracturing range of the carbon dioxide fracturing device;

[0013] Performing drilling construction of the directional drilling hole and the fracturing drilling hole according to the arrangement parameters of the directional drilling hole and the fracturing drilling hole;

[0014] Arranging a carbon dioxide fracturing device in the fracturing borehole and sealing the orifice of the fracturing borehole;

[0015] Starting the carbon dioxide fracturing device to fracture and weaken the interbedded gangue layer;

[0016] evaluating the weakened interlayer to obtain weakening evaluation data;

[0017] Based on the weakening assessment data, the arrangement parameters of the directional drilling holes, the fracturing drilling holes and the carbon dioxide fracturing device in the interbedded gangue layer are optimized.

[0018] The combined directional drilling and carbon dioxide fracturing method for weakening interbedded gangue in an embodiment of the present invention provides a free surface by arranging large-diameter directional drill holes within the interbedded gangue layer. This can enhance the carbon dioxide fracturing and weakening effect of the interbedded gangue layer during the fracturing and weakening process of the carbon dioxide fracturing device. A plastic zone is easily formed around the large-diameter directional drill hole, causing plastic deformation of the rock mass, and prone to microcracks and fracture. The free surface formed by the directional drilling leads to a redistribution of stress in the surrounding area, and stress concentration is easily generated around the directional drill hole, causing localized fracture. This embodiment organically combines directional drilling and carbon dioxide fracturing to achieve sufficient fracturing and weakening of hard interbedded gangue, reducing the negative impact of hard interbedded gangue on coal cutting by the shearer.

[0019] 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 extension distribution range of the interlayer.

[0020] 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 the plurality of the fracturing drill holes are spaced and alternately arranged in the second extension direction;

[0021] 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;

[0022] The effective fracturing ranges of the carbon dioxide fracturing devices arranged in the plurality of fracturing boreholes overlap to cover the interbedded gangue layer.

[0023] 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;

[0024] When the thickness of the interlayer is greater than 1000 mm, a plurality of the 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 the 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.

[0025] In some embodiments, the length of the directional drilling hole is 80m to 150m;

[0026] And / or, a branch drill hole is further provided in the interbedded gangue layer, 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.

[0027] 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 leaking from the orifice of the fracturing borehole after the chain fracturing device is activated;

[0028] In the step of starting the carbon dioxide fracturing device, the carbon dioxide fracturing devices in the plurality of fracturing boreholes are started simultaneously.

[0029] In some embodiments, the step of evaluating the weakened interlayer to obtain weakening evaluation data includes:

[0030] Detecting the inner wall of the directional borehole using an imaging device to obtain the degree of wall fragmentation and crack development of the directional borehole based on imaging information;

[0031] Based on the dielectric constant difference of the rock mass detected by borehole radar, the broken zones, cracks and cavities in the weakened interbedded gangue layer are identified;

[0032] The weakened interlayer is evaluated to obtain the degree of crushing of different sections in the interlayer.

[0033] In some embodiments, the step of optimizing the arrangement parameters of the directional drilling holes, the fracturing drilling holes, and the carbon dioxide fracturing device in the interbedded gangue layer based on the weakening assessment data comprises:

[0034] The crushing degree of the interbedded gangue layer is graded and divided into an over-crushed section, a well-crushed section and a section with underdeveloped fractures according to the crushing degree from high to low;

[0035] constructing a feature database based on the degree of crushing of different sections in the interbedded gangue layer, the occurrence parameters of the interbedded gangue layer, the layout parameters of the directional drilling holes in different sections in the interbedded gangue layer, the layout parameters of the fracturing drilling holes, and the layout parameters of the carbon dioxide fracturing device;

[0036] 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-fractured section and the underdeveloped fracture section are optimized to iteratively optimize the feature database.

[0037] The coal mining method according to an embodiment of the present invention comprises:

[0038] S1. Determine whether the thickness of the interlayer of coal in the coal seam is greater than a second threshold and whether the hardness of the interlayer of coal is greater than a third threshold;

[0039] S2. If yes, the gangue layer in the coal seam is weakened by using the combined directional drilling and carbon dioxide fracturing method as described in any of the above embodiments;

[0040] S3. Use coal mining machines to carry out coal mining operations.

[0041] In some embodiments, the coal mining method further comprises:

[0042] S4. When excavating to the next coal seam containing an interbedded gangue layer, repeat steps S1 to S3, and determine the layout parameters of the directional drilling holes, the layout parameters of the fracturing drilling holes, and the layout parameters of the carbon dioxide fracturing device in the interbedded gangue layer based on the iteratively optimized feature database. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the arrangement of directional drilling and fracturing drilling in an embodiment of the present invention.

[0044] Figure 2 The present invention is a flowchart of a method for weakening gangue by combining directional drilling with carbon dioxide fracturing according to an embodiment of the present invention.

[0045] Figure 3 4 is a flow chart of a coal mining method according to an embodiment of the present invention.

[0046] Reference numerals:

[0047] 1. Interlayer of gangue;

[0048] 2. Directional drilling;

[0049] 3. Fracture drilling;

[0050] 4. Cracks. DETAILED DESCRIPTION

[0051] The 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.

[0052] The following describes a method for weakening interbedded gangue and a coal mining method using directional drilling combined with carbon dioxide fracturing according to an embodiment of the present invention.

[0053] like Figure 1-Figure 3 As shown, the method for weakening interbedded gangue by combining directional drilling and carbon dioxide fracturing according to an embodiment of the present invention includes:

[0054] S101. Obtain the occurrence parameters of the interbedded gangue layer 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 information 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 interbedded gangue layer 1 can also be detected by geophysical exploration and drilling to obtain detection data. The occurrence parameters of the interbedded gangue layer 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 extension distribution range of the interbedded gangue layer 1. It is understandable that in order to improve the safety and controllability during the construction process, the surrounding environmental information of the interbedded gangue layer 1 can also be comprehensively judged through the above-mentioned information to reduce the disturbance to the surrounding environment.

[0055] S102. Based on the occurrence parameters of the interbedded gangue layer 1, determine the layout parameters of the directional drill hole 2, the fracturing drill hole 3, and the carbon dioxide fracturing device used to fracture and weaken the interbedded gangue layer 1. The radial dimension of the directional drill hole 2 is no less than 300 mm to form a free surface in the interbedded gangue layer 1. In this embodiment, the use of a large-diameter directional drill hole 2 can effectively form a free surface within the interbedded gangue layer 1, changing the stress distribution of the interbedded gangue layer 1 in the area surrounding the directional drill hole 2, thereby facilitating stress concentration around the directional drill hole 2 and causing localized fracture. The fracturing drill hole 3 is positioned adjacent to some of the directional drill holes 2 so that the directional drill holes 2 adjacent to the fracturing drill hole 3 are within the effective fracturing range of the carbon dioxide fracturing device.

[0056] In this embodiment, the distance "adjacent" refers to the radius of the effective fracturing range of the CO2 fracturing device placed within the fracturing borehole 3. In other words, the distance between the adjacent directional drill hole 2 and fracturing borehole 3 is less than the radius of the effective fracturing range of the CO2 fracturing device placed within the fracturing borehole 3, ensuring that the directional drill hole 2 is within the effective fracturing range of the CO2 fracturing device. The arrangement of the free surface enhances the fracturing and weakening effect of the CO2 fracturing device on the interbedded gangue layer 1.

[0057] It is understandable that the interlayer 1 is flat and extends in the circumferential direction. When no directional drilling hole 2 is set, the interlayer 1 is more easily broken in the thickness direction during the fracturing process, and the greater 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 up a 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 on the interlayer 1. At the same time, this embodiment can also reduce the filling amount of the carbon dioxide fracturing device.

[0058] 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 .

[0059] During the construction of directional drilling 2 and fracturing borehole 3, a directional drill rig and a mining rotary steerable drilling system can be used to drill through the hard interbedded gangue layer 1. The diameter of directional borehole 2 is no less than 300 mm to ensure a free surface of effective size. The diameter of fracturing borehole 3 is determined by the size of the CO2 fracturing device, ensuring that the outer wall of the CO2 fracturing device is in close contact with the inner wall of fracturing borehole 3 after the CO2 fracturing device is delivered into fracturing borehole 3.

[0060] The directional drill holes 2 and the fracturing drill holes 3 can be arranged at intervals and in an alternating pattern. It is understood that at least one directional drill hole 2 is arranged on opposite sides of each fracturing drill hole 3. 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.

[0061] S104 , placing a carbon dioxide fracturing device in the fracturing borehole 3 and sealing the orifice of the fracturing borehole 3 to prevent gas leakage from the orifice of the fracturing borehole 3 during the fracturing process, thereby improving the fracturing and weakening effect on the interlayer 1 .

[0062] S105: Activate the carbon dioxide fracturing device to fracture and weaken the interlayer 1, thereby generating cracks 4 in the interlayer 1 and achieving fragmentation. If multiple fracturing boreholes 3 are arranged in the interlayer 1, the carbon dioxide fracturing devices in the multiple fracturing boreholes 3 can be activated simultaneously or one by one.

[0063] S106: Evaluate the weakened interlayer 1 to obtain weakening evaluation data. The weakening evaluation data can reflect the crack development and breakage of the interlayer 1.

[0064] S107. Based on the weakening assessment data, optimize the layout parameters of the directional drill hole 2, the fracturing drill hole 3, and the CO2 fracturing device in the interlayer 1. It is understood that after the previous fracturing and weakening, by analyzing the weakening assessment data after the fracturing and weakening of the interlayer 1, it is possible to iteratively optimize the layout parameters in step S102, thereby helping to improve the effect of subsequent fracturing and weakening of the interlayer 1.

[0065] The combined directional drilling and carbon dioxide fracturing method for weakening interbedded gangue in an embodiment of the present invention provides a free surface by arranging a large-diameter directional drill hole 2 within the interbedded gangue layer 1. This enhances the carbon dioxide fracturing and weakening effect of the interbedded gangue layer 1 during the fracturing and weakening process by the carbon dioxide fracturing device. A plastic zone is easily formed around the large-diameter directional drill hole 2, causing plastic deformation of the rock mass, and prone to microcracks and fracture. The free surface formed by the directional drill hole 2 leads to a redistribution of stress in the surrounding area, and stress concentration is easily generated around the directional drill hole 2, causing localized fracture. This embodiment organically combines directional drilling 2 with carbon dioxide fracturing to achieve sufficient fracturing and weakening of hard interbedded gangue, reducing the negative impact of hard interbedded gangue on coal cutting by the shearer.

[0066] In this embodiment, carbon dioxide exists in a liquid state when its pressure is greater than 7.35 MPa and below 31°C. Above this temperature, it begins to vaporize, and its pressure fluctuates continuously with temperature, reaching a supercritical state. Exploiting this property, the main pipe of the fracturing device is filled with liquid carbon dioxide, and a detonator is used to rapidly ignite the liquid carbon dioxide. Within 40 milliseconds, the liquid carbon dioxide in the main pipe rapidly vaporizes, expanding its volume approximately 600 times. This produces a large amount of high-pressure carbon dioxide gas, which in turn generates stress waves that impact the target rock mass, achieving the desired fracture. Liquid carbon dioxide phase change fracturing is a physical blasting process that is more controllable and safer than traditional rock blasting methods.

[0067] The lack of free surfaces in intact, dense rock masses limits the scope of fracture weakening within the interlayer, making it difficult to fully fracture a large area of interlayers. The stress waves generated during the CO2 gasification process are reflected at the free surfaces as tensile waves, which help break up the interlayers. The presence of free surfaces makes this reflection more effective, thereby enhancing the efficiency and effectiveness of fracture weakening. The presence of free surfaces reduces the resistance of interlayers to the pressure generated during gasification, a process known as a clamping effect. This reduces the difficulty of breaking up interlayers and reduces the amount of CO2 required per unit volume.

[0068] The following describes some other specific embodiments of the present invention's combined directional drilling and carbon dioxide fracturing method for weakening interbedded gangue.

[0069] like Figures 1 to 3 As shown in FIG, the combined directional drilling and carbon dioxide fracturing method for weakening interbedded gangue includes:

[0070] S101. Obtain the occurrence parameters of the interbedded gangue layer 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 information 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 interbedded gangue layer 1 can also be detected by geophysical exploration and drilling to obtain detection data. The occurrence parameters of the interbedded gangue layer 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 extension distribution range of the interbedded gangue layer 1. It is understandable that in order to improve the safety and controllability during the construction process, the surrounding environmental information of the interbedded gangue layer 1 can also be comprehensively judged through the above-mentioned information to reduce the disturbance to the surrounding environment.

[0071] S102. Based on the occurrence parameters of the interbedded gangue layer 1, determine the layout parameters of the directional drill holes 2, the fracturing drill holes 3, and the carbon dioxide fracturing devices used to fracture and weaken the interbedded gangue layer 1. It will be understood that the interbedded gangue layer 1 has a first extension direction, a second extension direction, and a thickness direction. The directional drill holes 2 and the fracturing drill holes 3 are drilled along the first extension direction. Multiple directional drill holes 2 and multiple fracturing drill holes 3 are alternately arranged in the second extension direction. Each fracturing drill hole 3 is adjacent to a directional drill hole 2 on both sides of the second extension direction, so that each fracturing drill hole 3 forms a free surface 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 interbedded gangue layer 1.

[0072] The first extension direction can generally extend along the front-to-back direction in the diagram. For example, the first extension direction can generally be approximately aligned with the direction of coal seam mining. For another example, when the dip angle of the interbedded gangue layer is at a certain angle to the coal seam excavation direction, to ensure that the directional drill hole is located within the interbedded gangue layer, the first extension direction can be at a certain angle to the coal seam mining direction. The second extension direction can generally extend along the left-right direction in the diagram. For example, the second extension direction can generally extend along the radial direction of the mining face. The thickness direction can generally extend along the up-down direction in the diagram.

[0073] It can be understood that the first extension direction and the second extension direction are both approximately 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 can be orthogonal to each other.

[0074] 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 interbedded gangue layer 1 .

[0075] Preferably, when the thickness of the interlayer 1 is less than or equal to 1000 mm, the radial dimension of the directional drill hole 2 is 300 mm to 600 mm, and the directional drill hole 2 is located in the middle of the thickness direction of the interlayer 1. It is understood that the directional drill hole 2 is generally selected in an interlayer 1 with a thickness greater than 300 mm. However, when a large area of the interlayer 1 in the second extension direction has a thickness less than 300 mm, or when the thickness of the interlayer 1 in the first extension direction varies and is less than 300 mm, in order to improve the cracking and weakening effect of the interlayer 1, a portion of the large-diameter directional drill holes set in the interlayer 1 will be located in the coal seams on both sides of the interlayer 1 in the thickness direction.

[0076] When the thickness of the interlayer 1 is greater than 1000 mm, multiple directional drill holes 2 are arranged in groups along the thickness direction of the interlayer 1 to form a directional hole group. The sum of the radial dimensions of the multiple directional drill holes 2 in the directional hole group is 30% to 60% of the thickness of the interlayer 1. The fracturing drill holes 3 and the directional hole group are spaced apart in the second extension direction. At least some of the directional drill holes 2 in the directional hole group are located on either side of the fracturing drill holes 3 in the thickness direction. In other words, the multiple directional drill holes 2 in the directional hole group can be arranged approximately symmetrically along the thickness direction, thereby ensuring that an effective free surface of sufficient size and area is formed within the interlayer 1.

[0077] 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 slightly above the fracturing drill hole 3 in the thickness direction, and the other directional drill hole 2 is arranged slightly below the fracturing drill hole 3 in the thickness direction.

[0078] 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 of the directional drill holes 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.

[0079] It is understood that when the thickness of the interlayer 1 in the coal seam is relatively thin, the impact on the performance of the coal mining machine is minimal, and fracturing and weakening are not necessary. 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 combined directional drilling and carbon dioxide fracturing interlayer weakening method of this embodiment is suitable for interlayer 1 with a thickness of 300 mm to 2000 mm.

[0080] Furthermore, a branch drill hole is provided in the interbedded gangue layer 1, connected to the directional drill hole 2. The radial dimension of the branch drill hole is smaller than that of the directional drill hole 2. The branch drill hole extends toward the adjacent fracturing drill hole 3 and is not connected to the fracturing drill hole 3. When the thickness of a local section of the interbedded gangue layer 1 suddenly increases, the branch drill hole can be drilled into the side wall of the directional drill hole 2 to increase the free surface size of the corresponding section and enhance the fracturing weakening effect of the corresponding section.

[0081] 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 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.

[0082] In this embodiment, the use of a large-diameter directional drill hole 2 creates an effective free surface within the interlayer 1, altering the stress distribution of the interlayer 1 in the area surrounding the directional drill hole 2. This facilitates stress concentration around the directional drill hole 2, leading to localized fracture. The fracturing drill hole 3 is positioned adjacent to some of the directional drill holes 2, ensuring that the adjacent directional drill holes 2 are within the effective fracturing range of the CO2 fracturing device.

[0083] In this embodiment, the distance "adjacent" refers to the radius of the effective fracturing range of the CO2 fracturing device placed within the fracturing borehole 3. In other words, the distance between the adjacent directional drill hole 2 and fracturing borehole 3 is less than the radius of the effective fracturing range of the CO2 fracturing device placed within the fracturing borehole 3, ensuring that the directional drill hole 2 is within the effective fracturing range of the CO2 fracturing device. The arrangement of the free surface enhances the fracturing and weakening effect of the CO2 fracturing device on the interbedded gangue layer 1.

[0084] It is understandable that the interlayer 1 is flat and extends in the circumferential direction. When no directional drilling hole 2 is set, the interlayer 1 is more easily broken in the thickness direction during the fracturing process, and the greater 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 up a 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 on the interlayer 1. At the same time, this embodiment can also reduce the filling amount of the carbon dioxide fracturing device.

[0085] 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 .

[0086] During the construction of directional drilling 2 and fracturing borehole 3, a directional drill rig and a mining rotary steerable drilling system can be used to drill through the hard interbedded gangue layer 1. The diameter of directional borehole 2 is no less than 300 mm to ensure that a free surface of effective size is formed. The diameter of fracturing borehole 3 is determined based on the size of the CO2 fracturing device to ensure that the outer wall of the CO2 fracturing device is in close contact with the inner wall of fracturing borehole 3 after the CO2 fracturing device is delivered into fracturing borehole 3.

[0087] S104 , placing a carbon dioxide fracturing device in the fracturing borehole 3 and sealing the orifice of the fracturing borehole 3 to prevent gas leakage from the orifice of the fracturing borehole 3 during the fracturing process, thereby improving the fracturing and weakening effect on the interlayer 1 .

[0088] 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. The orifices of the fracturing borehole 3 are then blocked. The blocking length of the fracturing borehole 3 is greater than a first threshold value to reduce the amount of gas leaking from the orifices of the fracturing borehole 3 after the chain fracturing device is activated.

[0089] The first threshold value can be set according to the energy level after the fracturing device is activated, so as to reduce the gas leakage from the orifice of the fracturing borehole 3. For example, the first threshold value can be set to 1m to 2.5m.

[0090] S105 , starting the carbon dioxide fracturing device to fracture and weaken the interbedded gangue layer 1 . When a plurality of fracturing boreholes 3 are arranged in the interbedded gangue layer 1 , the carbon dioxide fracturing devices in the plurality of fracturing boreholes 3 can be started simultaneously or one by one.

[0091] S106: Evaluate the weakened interlayer 1 to obtain weakening evaluation data. The weakening evaluation data can reflect the crack development and breakage of the interlayer 1.

[0092] Specifically, the inner wall of the directional borehole 2 can be detected based on the imaging equipment, so as to obtain the degree of wall fragmentation and the development of cracks in the directional borehole 2 according to the imaging information.

[0093] Based on the dielectric constant difference of the rock mass detected by borehole radar, the fracture zones, cracks and cavities in the weakened interbedded gangue layer 1 were identified.

[0094] The weakened interlayer 1 is evaluated to obtain the degree of crushing of different sections in the interlayer 1. The performance of the coal mining machine is then combined to determine whether the weakened interlayer 1 is within the load-bearing range of the mechanical components.

[0095] S107. Based on the weakening assessment data, optimize the layout parameters of the directional drill hole 2, the fracturing drill hole 3, and the CO2 fracturing device in the interlayer 1. It is understood that after the previous fracturing and weakening, by analyzing the weakening assessment data after the fracturing and weakening of the interlayer 1, it is possible to iteratively optimize the layout parameters in step S102, thereby helping to improve the effect of subsequent fracturing and weakening of the interlayer 1.

[0096] Specifically, the degree of crushing of the interlayer 1 can be graded and divided into over-crushed sections, well-crushed sections and underdeveloped fissure sections according to the degree of crushing, from high to low. Among them, the over-crushed section may refer to the section where the interlayer 1 is weakened and is far below the maximum load that the mechanical parts of the coal mining machine can withstand. The well-crushed section may refer to the section where the interlayer 1 is weakened and is within the effective load range that the mechanical parts of the coal mining machine can withstand, which can ensure the normal and stable operation of the coal mining machine. The underdeveloped fissure section may refer to the section where the interlayer 1 has incomplete fissure development, and the coal mining machine will still bear a large load during excavation.

[0097] The over-crushed sections and well-crushed sections of the interlayer 1 indicate that the crushing and weakening effect of the interlayer 1 is good. However, the over-crushed section may indicate that there are 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.

[0098] The underdeveloped fracture sections may indicate that 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.

[0099] A feature database is constructed based on the degree of fragmentation in different sections of the interlayer 1, the occurrence parameters of the interlayer 1, the layout parameters of the directional drill holes 2 in different sections of the interlayer 1, the layout parameters of the fracturing drill holes 3, and the layout parameters of the CO2 fracturing device. This feature database can establish matching layout parameters for interlayer 1 with different occurrence parameters to guide subsequent interlayer weakening processes.

[0100] The layout parameters of directional drilling holes 2, fracturing drilling holes 3, and CO2 fracturing devices corresponding to over-fractured and underdeveloped fractured sections are optimized to iteratively optimize the feature database. This embodiment, through iterative optimization of the feature database, optimizes drilling parameters, CO2 fracturing device filling parameters, and other parameters, thereby reducing construction costs, improving work efficiency, and enhancing fracturing and weakening effects.

[0101] The combined directional drilling and CO2 fracturing method for weakening interbedded rock in an embodiment of the present invention provides a free surface by arranging a large-diameter directional drill hole 2 within the interbedded rock layer 1. This enhances the CO2 fracturing effect during the fracturing and weakening of the interbedded rock layer 1 by the CO2 fracturing device. A plastic zone easily forms around the large-diameter directional drill hole 2, causing plastic deformation of the rock mass and the development of microcracks and fractures. The free surface formed by the directional drill hole 2 leads to a redistribution of stress in the surrounding area, which can easily lead to stress concentration around the directional drill hole 2 and cause localized fracture. This embodiment organically combines directional drilling 2 with CO2 fracturing to achieve sufficient fracturing and weakening of hard interbedded rock, reducing the negative impact of hard interbedded rock on coal cutting by shearers. Furthermore, it is possible to iteratively optimize the layout parameters of the directional drill hole 2, the fracturing drill hole 3, and the CO2 fracturing device used to fracture and weaken the interbedded rock layer 1, thereby improving subsequent operational efficiency and effectiveness.

[0102] The coal mining method according to an embodiment of the present invention comprises:

[0103] 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.

[0104] Preferably, the second threshold value can be 250mm to 350mm. In other words, when the hardness of the gangue layer 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 gangue weakening method of the combined directional drilling and carbon dioxide fracturing of the embodiment of the present invention can be used to perform gangue weakening treatment.

[0105] Preferably, the third threshold value can 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 of the combined directional drilling and carbon dioxide fracturing of the embodiment of the present invention can be used to perform gangue weakening treatment.

[0106] S2. If yes, adopt the combined directional drilling and carbon dioxide fracturing method as described in any of the above embodiments to weaken the interbedded gangue layer 1 in the coal seam. The weakening treatment of the interbedded gangue layer 1 in this embodiment is the same as that in the above embodiments, and the effects thereof will not be described in detail.

[0107] S3. Use coal mining machines to carry out coal mining operations.

[0108] S4. When excavating to the next coal seam containing the interbedded gangue layer 1, repeat steps S1 to S3, and based on the feature database after iterative optimization, determine the layout parameters of the directional drilling hole 2 in the interbedded gangue layer 1, the layout parameters of the fracturing drilling hole 3, and the layout parameters of the carbon dioxide fracturing device.

[0109] 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 to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0110] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0111] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0112] In the present invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" 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 specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification, as well as features of different embodiments or examples, unless they are mutually inconsistent.

[0113] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for weakening interbedded gangue by combining directional drilling and carbon dioxide fracturing, characterized in that: include: Obtain the occurrence parameters of interbedded gangue layers in coal seams; Determining, based on the occurrence parameters of the interbedded gangue layer, the arrangement parameters of the directional drill hole, the fracturing drill hole, and the carbon dioxide fracturing device used to fracture and weaken the interbedded gangue layer in the interbedded gangue layer, wherein the radial dimension of the directional drill hole is not less than 300 mm to form a free surface in the interbedded gangue layer, 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 within the effective fracturing range of the carbon dioxide fracturing device; Performing drilling construction of the directional drilling hole and the fracturing drilling hole according to the arrangement parameters of the directional drilling hole and the fracturing drilling hole; Arranging a carbon dioxide fracturing device in the fracturing borehole and sealing the orifice of the fracturing borehole; Starting the carbon dioxide fracturing device to fracture and weaken the interbedded gangue layer; evaluating the weakened interlayer to obtain weakening evaluation data; Based on the weakening assessment data, optimizing the arrangement parameters of the directional drilling holes, the fracturing drilling holes and the carbon dioxide fracturing device in the interbedded gangue layer; The step of optimizing the arrangement parameters of the directional drilling holes, the fracturing drilling holes and the carbon dioxide fracturing device in the interbedded gangue layer based on the weakening assessment data comprises: The crushing degree of the interbedded gangue layer is graded and divided into an over-crushed section, a well-crushed section and a section with underdeveloped fractures according to the crushing degree from high to low; constructing a feature database based on the degree of crushing of different sections in the interbedded gangue layer, the occurrence parameters of the interbedded gangue layer, the layout parameters of the directional drilling holes in different sections in the interbedded gangue layer, the layout parameters of the fracturing drilling holes, and the layout parameters of the carbon dioxide fracturing device; Optimizing the layout parameters of directional drilling holes, fracturing drilling holes, and carbon dioxide fracturing devices corresponding to the over-fractured section and the underdeveloped fracture section, so as to iteratively optimize the feature database; The length of the directional drilling hole is 80m to 150m; And / or, a branch drill hole is further provided in the interbedded gangue layer, 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.

2. The method for weakening interbedded 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 interbedded gangue layer in the coal seam includes collecting coal mine production geological data, detecting the interbedded gangue layer through 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 interbedded gangue layer, wherein the occurrence parameters include at least the number of layers, thickness, hardness and extension distribution range of the interbedded gangue layer.

3. The method for weakening interbedded 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 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 interbedded gangue layer.

4. The method for weakening interbedded gangue by combining directional drilling and carbon dioxide fracturing according to claim 3, 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, a plurality of the 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 the 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 interbedded 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 leaking 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.

6. The method for weakening interbedded 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 using an imaging device to obtain the degree of wall fragmentation and crack development of the directional borehole based on imaging information; Based on the dielectric constant difference of the rock mass detected by borehole radar, the broken zones, cracks and cavities in the weakened interbedded gangue layer are identified; The weakened interlayer is evaluated to obtain the degree of crushing of different sections in the interlayer.

7. A coal mining method, characterized in that: include: S1. Determine whether the thickness of the interlayer of coal in the coal seam is greater than a second threshold and whether the hardness of the interlayer of coal is greater than a third threshold; S2. If yes, the interlayer in the coal seam is weakened by using the combined directional drilling and carbon dioxide fracturing method according to any one of claims 1 to 6; S3. Use coal mining machines to carry out coal mining operations.

8. The coal mining method according to claim 7, characterized in that: Also includes: S4. When excavating to the next coal seam containing an interbedded gangue layer, repeat steps S1 to S3, and determine the layout parameters of the directional drilling holes, the layout parameters of the fracturing drilling holes, and the layout parameters of the carbon dioxide fracturing device in the interbedded gangue layer based on the iteratively optimized feature database.

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