A method for constructing a transparent working face of soft coal seam based on a floor directional comb hole

Abstract

This invention discloses a method for constructing a transparent working face in a fractured and soft coal seam based on directional comb-shaped boreholes in the bottom plate, comprising: Step 1: obtaining modeling data sources through geological exploration and constructing an initial geological model of the working face; Step 2: designing directional comb-shaped boreholes in the coal mine floor, conducting directional drilling and collecting drilling data; Step 3: obtaining lithological stratification curves based on the drilling data, and combining the lithological stratification curves with the borehole trajectory to obtain a dataset of the top and bottom interfaces of the target layer; Step 4: based on the stratification, extracting the locations of structures on the actual drilling trajectory of each borehole and correcting the initial geological model of the working face, combining the corrected structures within the target layer to form a dataset of structures; Step 5: drawing a three-dimensional spatial distribution based on the dataset of the top and bottom interfaces of the target layer and the dataset of structures. This invention can precisely detect the coal seam interface and the internal structure of the coal seam, construct a transparent working face, and provide precise detection data for intelligent mining.

Description

Technical Field

[0001] This invention relates to the field of directional drilling and intelligent mining technology in underground coal mines, specifically to a method for constructing a transparent working face in soft and fractured coal seams based on directional comb-shaped holes in the bottom plate. Background Technology

[0002] The use of bottom-plate comb-shaped long borehole technology, with the main borehole positioned in a suitable directional drilling layer with good porosity, and branch holes extending into the coal seam, solves the problems of large drilling volume and low utilization rate of effective borehole sections in the pre-mining gas extraction method for coal seam strips using dense cross-layer drilling in bottom-plate rock roadways. Positioning the main borehole above hard rock strata avoids the need for all cross-layer boreholes to penetrate hard rock layers, saving time for pre-gas extraction in coal seams. Furthermore, bottom-plate comb-shaped boreholes can replace gas extraction boreholes in the coal seam to be mined, achieving advanced gas control in the coal seam to be mined. In addition, this technology employs directional drilling, solving the problem of difficult long-distance in-seam drilling under complex geological conditions, providing a guarantee for working face succession and safe mine production. Currently, the bottom comb-shaped directional long borehole is only used for gas drainage and is not fully utilized. During the drilling process of the bottom comb-shaped directional long borehole, the direction of coal and rock undulations, geological anomalies, and the location of water hazards can be detected to form a transparent working face, providing more detailed geological conditions and disaster forecasts for subsequent precision coal mining.

[0003] The existing technology has the following drawbacks:

[0004] Compared to conventional drilling techniques, long-distance comb-shaped directional drilling technology for the underground coal mine floor allows for real-time measurement of borehole trajectory, dynamic control of borehole deviation, and exploration of the coal seam roof and floor through branch holes. It can achieve decimeter-level accuracy in detecting coal seam roof and floor elevations, coal thickness variations, and geological anomalies. Currently, most methods for achieving transparent working faces are based on geophysical exploration, and the data obtained from directional drilling has not been effectively utilized. However, the results of directional drilling exploration of the working face's geological conditions can be used to achieve working face transparency, providing a high-precision geological model for intelligent coal mining. Summary of the Invention

[0005] The purpose of this invention is to provide a method for constructing a transparent working face in a soft, fractured coal seam based on directional comb-shaped boreholes in the bottom plate. The technical problem to be solved is to use the accurate drilling data obtained by long-distance comb-shaped directional drilling in the bottom plate to correct the working face geological model established based on the initial geological exploration engineering data, thereby forming a transparent working face of the coal seam to be mined.

[0006] A method for constructing a transparent working face in a fractured and soft coal seam based on directional comb-shaped holes in the bottom plate includes:

[0007] Step 1: Obtain modeling data through geological exploration and construct the initial geological model of the working face;

[0008] Step 2: Design directional comb-shaped holes for the underground floor of the coal mine, conduct directional drilling, and collect drilling data;

[0009] The aforementioned directional comb-shaped holes in the coal mine underground floor include main holes and branch holes. The opening angle of the main hole is 5 to 10° greater than the dip angle of the floor rock strata, and the sandstone stratum is selected as the extension layer of the main hole.

[0010] The branch hole enters the coal seam from the reserved branch point of the main hole, and obtains a coal seam bottom exploration point. It continues to smoothly pass through the coal seam along the drilling trajectory to explore the roof and obtain a roof exploration point. The secondary branch hole for roof exploration and the secondary branch hole for bottom exploration are carried out alternately.

[0011] Step 3: Obtain the lithological stratification curve based on the drilling data. Combine the lithological stratification curve with the borehole trajectory to obtain the target layer top and bottom interface dataset.

[0012] Step 4: Based on the layering, extract the location of structures on the actual drilling trajectory of each borehole and correct the initial geological model of the working face. Combine the corrected structures in the target layer to form a dataset of structures.

[0013] Step 5: Draw the three-dimensional spatial distribution based on the target layer top and bottom interface dataset and the constructed dataset.

[0014] Optionally, the bending strength of the drilling trajectory of the main hole shall not exceed 1° / 3m; the spacing between adjacent bottom-exploring secondary branch holes or top-exploring secondary branch holes shall be maintained at 3 to 5m.

[0015] Optionally, under the premise of meeting the requirements of gas drainage, the spacing between main boreholes should be controlled at 5 to 10 m. The main boreholes should be constructed by advancing and branching. When designing the trajectory, branch points should be reserved at certain intervals. The spacing between branch points should not be greater than the extension distance of the branch borehole in the coal seam.

[0016] Optionally, when the coal seam thickness is greater than 5m and the difference in coal and rock properties f coefficients along the coal seam thickness direction exceeds 0.3, the branch holes are arranged on the side with better hole formation stability; the number of secondary branch holes is the ratio of the maximum extension distance of the branch holes to the spacing between the secondary branch holes.

[0017] Optionally, when the permeability of the coal seam to be extracted is extremely poor, resulting in a borehole extraction influence radius of less than 3m, and there is still a extraction coverage blind zone even with a main borehole spacing of 5m, the first top-exploring secondary branch borehole after the branch borehole enters the coal seam is arranged slightly to the left or right along the borehole trajectory, and the next top-exploring secondary branch borehole is arranged accordingly to the right or left. The bottom-exploring branch borehole is arranged in the same way. The borehole spacing is 2 to 3m and does not exceed the extraction influence range. At the same time, the secondary branch boreholes on the left and right sides should be able to overlap to avoid exploration and extraction blind zones in the direction of advancement.

[0018] Optionally, the directional drilling in step 2 includes:

[0019] Step 1: Connect the drill bit, bottom hole motor, lower non-magnetic drill rod, measuring probe, upper non-magnetic drill rod, lower insulated drill rod, drill rod, water pump, and other drilling tools and measuring instruments in sequence, and connect the water pump and prepare the drilling rig.

[0020] Step 2: Turn on the explosion-proof computer and water pump for drilling trajectory measurement, start the drilling rig to perform directional drilling of the main hole in the bottom rock strata, and after drilling to the designed branch point, perform the first main branch hole forward branching, and continue drilling the top and bottom secondary branch holes;

[0021] Step 3: The measuring probe is used to measure the borehole trajectory information, which is recorded and stored by the drilling rig's explosion-proof computer. During the drilling process, the backfill situation is monitored to determine changes in lithology and record them in a timely manner.

[0022] Step 4: The first branch hole should be used to initially investigate the condition of the top and bottom of the target coal seam. If the actual drilling results show a large discrepancy with the initial geological model, the design of subsequent main holes and branch holes should be adjusted in a timely manner based on the actual drilling results.

[0023] Step 5: After completing the construction of the first branch hole, pull the drill bit back to the main hole and continue the construction of the main hole and subsequent branch holes;

[0024] Step Six: After completing all branch drilling operations, lift the drill and retrieve the stored data measured inside the hole;

[0025] Step 7: Adjust the design of the remaining boreholes based on the construction data of the first borehole, and repeat steps 1 to 6 to complete the construction of the remaining designed boreholes. Then, extract the drilling data of each borehole.

[0026] Optionally, step 3, obtaining the lithological stratification curve based on drilling data, includes:

[0027] The boundary points of the target layer on the borehole trajectory are extracted to form a top and bottom interface boundary point dataset. Then, the layered dataset is processed, the boundary points of each layer are connected, and a lithological stratification curve is established.

[0028] Optionally, the processing method of the layered dataset is to divide the target layer into grids along the vertical plane of the layer height, thereby determining the x and y coordinates of each grid point. The z coordinate data of the top and bottom interfaces of each grid point are obtained by interpolation of its three nearest measured points, and the distance between adjacent grid points is 2 to 3 m.

[0029] Optionally, use the top plate grid point W ij (x ij y ij , z ij For example, the z-axis coordinate of the top plate of the grid point is z. ij The interpolation calculation method is as follows: the coordinates of the three nearest adjacent actual exposed roof interface points are M.D1 (x D1 y D1 , z D1 M D2 (x D2 y D2 , z D2 M D3 (x D3 y D3 , z D3 The direction vectors M of the two points D1 M D2 =(x D2 -x D1 y D2 -y D1 , z D2 -z D1 M D1 M D3 =(x D3 -x D1 y D3 -y D1 , z D3 -z D1 If we replace the points with a = (a1, a2, a3) and b = (b1, b2, b3) respectively, then the normal vector of the three points coplanar is n = a × b = (a2b3 - a3b2, a3b1 - a1b3, a1b2 - a2b1). Then, based on the plane normal vector n and the grid points W on the plane... ij (x ij y ij , z ij The point-normal form of the plane equation is:

[0030] (a2b3-a3b2)·(x i -x D1 )+(a3b1-a1b3)·(y i -y D1 )+(a1b2-a2b1)·(z i -z D1 ) = 0, and finally, based on the x-axis of the desired point... ij y ij Value, substitute into the formula to solve z ij The value is sufficient;

[0031] Similarly, the coordinates of its three nearest adjacent actual exposed base plate interface points are M. d1 (x d1 y d1 , z d1 M d2 (x d2 y d2 , z d2 Md3 (x d3 y d3 , z d3 If the base plate grid point W′ is... ij The base plate z-axis coordinate z′ ij The interpolation calculation method is as follows: the direction vectors M of the two points... d1 M d2 =(x d2 -x d1 y d2 -y d1 , z d2 -z d1 ),

[0032] M d1 M d3 =(x d3 -x d1 y d3 -y d1 , z d3 -z d1 If we replace the points with a′=(a′1,a′2,a′3) and b′=(b′1,b′2,b′3) respectively, then the normal vector of the three points coplanar is n′=a′×b′=(a′2b′3-a′3b′2,a′3b′1-a′1b′3,a′1b′2-a′2b′1). Then, based on the plane normal vector n′ and the grid points W′ on the plane... ij (x ij y ij , z′ ij The point-normal form of the plane equation is:

[0033] (a′2b′3-a′3b′2)·(x j -x d1 )+(a′3b′1-a′1b′3)·(y j -y d1 )+(a′1b′2-a′2b′1)·(z j -z d1 ) = 0, and finally, based on the x-axis of the desired point... ij y ij Substitute the value into the formula to solve for z′. ij The value is sufficient;

[0034] The target layer top and bottom interface dataset is obtained through the above data processing.

[0035] Optionally, step 4 specifically includes: precise exploration of known structures, identifying unknown structures encountered during drilling and extracting the location of structures on each borehole trajectory, and combining known and unknown structures within the target layer to form a dataset of structures.

[0036] Compared with the prior art, the beneficial technical effects of this invention are:

[0037] Based on directional drilling technology, this invention offers high accuracy in identifying strata lithology and structures. Multiple sets of bottom comb-shaped boreholes are arranged in the bottom strata of the target layer. These comb-shaped boreholes can be used to preemptively control gas in the working face area, and the branch boreholes can be used to precisely detect the coal seam interface and internal coal seam structures (collapse columns, faults, etc.), thus creating a transparent working face and providing precise detection data for intelligent mining. Attached Figure Description

[0038] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0039] Figure 1 This is a schematic cross-sectional view of the directional comb-shaped drilling construction and drilling of the base plate according to the present invention;

[0040] Figure 2 This is a schematic diagram of the target working surface grid point data processing of the present invention;

[0041] The labels in the diagram represent:

[0042] 1-Grid point; 2-Horizontal interval; 3-Vertical interval; 4-Coordinates of the top and bottom plates to be determined; 5-Coordinates of the actual exposed top plate; 6-Coordinates of the actual exposed bottom plate. Detailed Implementation

[0043] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The terms used in this invention are explained below:

[0044] In this invention, lithological stratification and structure refer to the following: a layer is the basic unit that makes up sedimentary strata, composed of rocks with essentially the same composition. Coal seams are layered solid combustible minerals formed from plant remains through complex biochemical and geological processes. They are found within coal-bearing rock formations, located between the top and bottom sedimentary rocks, which are generally mudstone, shale, sandstone, and limestone. The structure of coal-bearing strata mainly refers to the morphology of the coal seam and its surrounding rock strata under geological forces, including monoclines, folds, and faults.

[0045] The method for constructing a transparent working face in a coal mine based on directional comb-shaped holes in a base plate, as described in this invention, mainly includes the following steps.

[0046] Step 1: Collect data from previous geological exploration projects as the data source for modeling to construct the initial geological model of the working face. The data from these geological exploration projects includes a wealth of geological information obtained from surface drilling, detailed tunnel positioning and mapping, channel seismic exploration, gas extraction well logging, and the positioning and mapping of the working face. The initial geological model of the working face mainly includes the top and bottom interfaces of the target layer, structural regions, etc.

[0047] Step 2: Design directional comb-shaped holes for the underground floor of the coal mine, conduct directional drilling, and collect drilling data.

[0048] Combination Figure 1 Step 2, the design of directional comb-shaped boreholes in the underground coal mine floor, should include the design of main boreholes and branch boreholes. The opening angle of the main borehole is generally 5-10° greater than the dip angle of the floor strata. Straight drilling is recommended for opening the borehole. After encountering the floor strata, the drilling angle should be reduced. The bending strength of the borehole design trajectory should not be too high, generally not exceeding 1° / 3m. The design and layout of the main borehole should be as close as possible to the pre-extracted coal seam, provided that it meets the requirements for suitable directional drilling and good borehole formation, in order to reduce the rock-crossing section of the branch boreholes. For coal-bearing strata, stable sandstone layers are generally selected as the main type. When drilling into a stable stratum, the borehole trajectory inclination is adjusted to align with the stable stratum. Generally, the borehole trajectory axis should be 0.5m away from the top of the stable stratum. The spacing between adjacent main boreholes should be determined based on the influence radius of the boreholes in the coal seam to be extracted. While meeting gas extraction requirements, the main borehole spacing should be controlled between 5 and 10m, which is the interval between the trajectories of two adjacent main boreholes. The main boreholes are constructed using a forward-branching method. When designing the trajectory, branch points should be reserved at certain intervals, with the spacing between branch points not exceeding the extension distance of the branch borehole within the coal seam. The advantage of placing the main boreholes in the floor strata is that it avoids the problem of poor borehole formation and collapse during long directional drilling in soft coal seams. Entering the coal seam through multiple branch boreholes significantly reduces the drilling length encountered by a single branch borehole, thus improving the coal seam encounter rate and borehole formation rate. The design principle of branch holes is that their location and number should be able to cover the coal seam in the entire direction of the main hole to avoid coal seam coverage blind spots. At the same time, the need for geological transparency should be taken into account to explore the top and bottom of the coal seam as much as possible and to explore the structural conditions.

[0049] Specifically, in step 2, the branch holes of the directional comb-shaped boreholes in the underground coal mine floor are designed as fishbone-type branch holes. The specific construction method is as follows: the branch hole enters the coal seam from the pre-reserved branch point of the main hole, obtaining a coal seam floor exploration point. It continues to smoothly penetrate the coal seam along the drilling trajectory to explore the roof, obtaining a roof exploration point. At this time, the corrected positions of the roof and floor around the main branch hole are obtained. The drill bit is pulled back to the middle of the coal seam to advance the main branch hole to open the secondary branch hole. After opening the secondary branch to explore the floor, the drill bit is pulled back to open the secondary branch to explore the roof. The fishbone pattern is formed by advancing the secondary branch to explore the roof and floor in sequence. The exploration of secondary branch holes is carried out alternately, with top and bottom secondary branch holes. The distance between adjacent top or bottom secondary branch holes should be maintained at about 3-5m. Extending the branch holes to the middle strata of the coal seam can reduce the difference in extension distance, improve the construction efficiency of secondary branch holes, and enhance the overall hole formation stability. When encountering a thick coal seam (generally greater than 5m) with significant differences in coal and rock properties along the thickness direction (generally a difference in f-coefficient exceeding 0.3), and significant differences in hole formation stability between upper and lower strata, the branch holes should be arranged closer to the side with better hole formation stability. The number of fishbone-shaped secondary branch holes formed by each branch hole should be determined based on the hole formation conditions of the fractured and soft coal seam to ensure the hole formation stability. Fractured and soft coal seams with good hole formation properties can have more secondary branch holes, the number being the ratio of the maximum extension distance of the branch hole to the distance between the secondary branch holes. After completing one fishbone-shaped branch hole, the drill string is pulled back to the main hole at the bottom plate, and drilling continues forward to the next designed branch point for the construction of the next fishbone-shaped branch hole. The above fishbone-style branch hole arrangement should be as close as possible to the transverse direction within the longitudinal profile of the coal seam to ensure that the branch hole spacing between adjacent main holes is consistent.

[0050] When the permeability of the coal seam to be extracted is extremely poor, making the radius of influence of borehole extraction less than 3m, and the 5m interval between main boreholes is still too large to meet the extraction requirements, a fishbone-style branch borehole can be used to cover the transverse profile of the coal seam and avoid extraction blind spots. Specifically, after the main branch borehole enters the coal seam, the first set of top (bottom) exploration secondary branch boreholes is arranged slightly to the left (right) of the trajectory's forward direction, and the next set of top (bottom) exploration secondary branch boreholes is arranged accordingly to the right (left). For example, normal branch boreholes and secondary branch boreholes should be coplanar in the vertical plane. Figure 1 (This is a vertical plane projection diagram), meaning the borehole trajectory projection in the horizontal plane is neither deflected to the left nor to the right. Here, to cover a certain area to the left and right in the horizontal plane and eliminate extraction blind spots, the projection of the first top-exploration secondary branch hole in the horizontal plane is deflected to the left, and the projection of the next top-exploration secondary branch hole in the horizontal plane is deflected to the right. Similarly, the projection of the first bottom-exploration secondary branch hole in the horizontal plane is deflected to the right, and the projection of the next bottom-exploration secondary branch hole in the horizontal plane is deflected to the left. The interval between the two sets is generally about 2 meters and does not exceed the extraction influence range. At the same time, the secondary branch holes on the left and right sides should be able to overlap to avoid exploration and extraction blind spots in the direction of advancement.

[0051] Specifically, the drilling data in step 2 includes: borehole trajectory, lithological changes, and structural conditions.

[0052] Specifically, step 2, directional drilling, includes: Step 1: sequentially connecting the drill bit, bottom hole motor, lower non-magnetic drill rod, measuring probe, upper non-magnetic drill rod, lower insulated drill rod, drill rod, water pump, and other drilling tools and measuring instruments, and connecting the water pump and preparing the drilling rig;

[0053] Step 2: Turn on the explosion-proof computer and water pump for drilling trajectory measurement, start the drilling rig to perform directional drilling of the main hole in the bottom rock strata, and after drilling to the designed branch point, perform the first main branch hole forward branch opening, and continue drilling the first fishbone branch hole;

[0054] Step 3: The measuring probe is used to measure the borehole trajectory information, which is recorded and stored by the drilling rig's explosion-proof computer. During the drilling process, the backfill situation is monitored to determine changes in lithology and record them in a timely manner.

[0055] Step 4: The first main branch hole should be used to initially investigate the condition of the top and bottom of the target coal seam. If the actual drilling results show a large discrepancy with the initial geological model, the design of subsequent main holes and branch holes should be adjusted in a timely manner based on the actual drilling results.

[0056] Step 5: After completing the construction of the first herringbone branch hole, pull the drill bit back to the main hole and continue the construction of the main hole and subsequent herringbone branch holes.

[0057] Step Six: After completing all branch drilling operations, lift the drill and retrieve the stored data measured inside the hole;

[0058] Step 7: Adjust the design of the remaining boreholes based on the construction data of the first borehole, and repeat steps 1 to 6 to complete the construction of the remaining designed boreholes. Then, extract the drilling data of each borehole.

[0059] Step 3: Process and analyze the obtained drilling data to obtain lithological stratification curves, and combine the lithological curves with the borehole trajectory to obtain the target layer top and bottom interface dataset.

[0060] Specifically, step 3, drilling data preprocessing, involves the first step after completing directional drilling and obtaining drilling data. The preprocessing includes the unified transformation of the coordinate system and zero point of the borehole trajectory data, the confirmation of the trajectory points corresponding to the exposed lithological strata and structures, and the correction of abnormal data.

[0061] Specifically, in step 3, lithological stratification features are extracted. After completing the drilling data preprocessing, the boundary points of the target layer on the borehole trajectory are extracted to form a top and bottom interface boundary point dataset. Then, the stratified dataset is processed, the boundary points of each layer are connected, and a stratification curve is established.

[0062] Combination Figure 2The processing method for the layered dataset is as follows: the target layer is divided into grids along the vertical plane of the layer height, which determines the x and y coordinates of each grid point 1, the horizontal interval 2 and the vertical interval 3. The z coordinate data of the top and bottom interfaces of each grid point are calculated by interpolation of its three nearest measured points; for example, the coordinates of the top and bottom plates to be determined are 4, the actual exposed top plate coordinates are 5 and the actual exposed bottom plate coordinates are 6. The spacing between adjacent grid points is generally controlled at about 2m. When there are many actual exposed points, the spacing can be further increased.

[0063] With top plate grid point W ij (x ij y ij , z ij For example, the z-axis coordinate of the top plate of the grid point is z. ij The interpolation calculation method is as follows: the coordinates of the three nearest adjacent actual exposed roof interface points are M. D1 (x D1 y D1 , z D1 M D2 (x D2 y D2 , z D2 M D3 (x D3 y D3 , z D3 The direction vectors M of the two points D1 M D2 =(x D2 -x D1 y D2 -y D1 , z D2 -z D1 M D1 M D3 =(x D3 -x D1 y D3 -y D1 , z D3 -z D1 If we replace the points with a = (a1, a2, a3) and b = (b1, b2, b3) respectively, then the normal vector of the three points coplanar is n = a × b = (a2b3 - a3b2, a3b1 - a1b3, a1b2 - a2b1). Then, based on the plane normal vector n and the grid points W on the plane... ij (x ij y ij , z ij The point-normal form of the plane equation is:

[0064] (a2b3-a3b2).(x i -x D1 )+(a3b1-a1b3).(y i -yD1 )+(a1b2-a2b1)·(z i -z D1 ) = 0, and finally, based on the x-axis of the desired point... ij y ij Value, substitute into the formula to solve z ij The value is sufficient;

[0065] Similarly, the base plate grid point W′ ij (x ij y ij , z′ ij The coordinates of its three nearest adjacent actual exposed base plate interface points are M. d1 (x d1 y d1 , z d1 M d2 (x d2 y d2 , z d2 M d3 (x d3 y d3 , z d3 If the base plate grid point W′ is... ij The base plate z-axis coordinate z′ ij The interpolation calculation method is as follows: the direction vectors M of the two points... d1 M d2 =(x d2 -x d1 y d2 -y d1 , z d2 -z d1 ),

[0066] M d1 M d3 =(x d3 -x d1 y d3 -y d1 , z d3 -z d1 If we replace the points with a′=(a′1,a′2,a′3) and b′=(b′1,b′2,b′3) respectively, then the normal vector of the three points coplanar is n′=a′×b′=(a′2b′3-a′3b′2,a′3b′1-a′1b′3,a′1b′2-a′2b′1). Then, based on the plane normal vector n′ and the grid points W′ on the plane... ij (x ij y ij , z′ ij The point-normal form of the plane equation is:

[0067] (a′2b′3-a′3b′2)·(x j-x d1 )+(a′3b′1-a′1b′3)·(y j -y d1 )+(a′1b′2-a′2b′1), (z j -z d1 ) = 0, and finally, based on the x-axis of the desired point... ij y ij Substitute the value into the formula to solve for z′. ij The value is sufficient;

[0068] The target layer top and bottom interface dataset is obtained through the above data processing.

[0069] Step 4: Based on the layering, extract the location of the structure on the actual drilling trajectory of each borehole and correct the structure of the initial model. Combine the corrected structures in the target layer to form a dataset of structures.

[0070] Specifically, step 4 includes: precise exploration of known structures and identification of unknown structures. For the structure distribution area in the target layer obtained from previous exploration, precise exploration is carried out by drilling. For the unknown structures encountered during drilling, the structure is identified and the location of the structure on each drilling trajectory is extracted. The structures in the target layer are combined to form a structure dataset.

[0071] Step 5: Based on the target layer top and bottom interface dataset and the constructed dataset, draw the distribution in three-dimensional space to make the geological conditions of the working face to be mined transparent.

[0072] Specifically, in step 5, a three-dimensional transparent working surface is constructed. The datasets obtained above are input into the three-dimensional drawing software. First, the coordinate positions of each dataset are loaded. Then, the interpolation algorithm is used to generate the curved surfaces of each layer and the construction interface. Finally, a three-dimensional geological model of the target layer area is obtained.

[0073] The preferred embodiments described above in conjunction with the accompanying drawings are preferred but not intended to limit the invention. The various specific technical features described above can be combined in any suitable form without contradiction, and this invention will not elaborate on them one by one. Any simple modifications or alterations made by those skilled in the art, such as arbitrary combinations or equivalent substitutions, to the technical solutions without departing from the scope of the technical solutions do not affect the essence of the technical solutions and still fall within the protection scope of the technical solutions represented by the embodiments of this invention.

Claims

1. A method for constructing a transparent working face in a fractured and soft coal seam based on directional comb-shaped holes in the bottom plate, characterized in that, include: Step 1: Obtain modeling data through geological exploration and construct the initial geological model of the working face; Step 2: Design directional comb-shaped boreholes for the coal mine floor, conduct directional drilling, and collect drilling data. The directional comb-shaped boreholes for the coal mine floor include a main borehole and branch boreholes. The opening angle of the main borehole is 5-10° greater than the dip angle of the floor strata, and sandstone is selected as the extension layer for the main borehole. The branch boreholes penetrate the coal seam from the pre-reserved branch point of the main borehole, obtaining a coal seam floor exploration point. They continue to smoothly penetrate the coal seam along the drilling trajectory to the roof, obtaining a roof exploration point. The secondary branch holes for roof exploration and secondary branch holes for bottom exploration are alternately advanced. The bending intensity of the drilling trajectory of the main borehole does not exceed 1° / 3m. The spacing between adjacent secondary branch holes for bottom exploration or roof exploration is maintained at 3-5m. Directional drilling includes: Step 1: Connect the drill bit, bottom hole motor, lower non-magnetic drill rod, measuring probe, upper non-magnetic drill rod, lower insulated drill rod, drill rod, water pump, and other drilling tools and measuring instruments in sequence, and connect the water pump and prepare the drilling rig. Step 2: Turn on the explosion-proof computer and water pump for drilling trajectory measurement, start the drilling rig to perform directional drilling of the main hole in the bottom rock strata, and after drilling to the designed branch point, perform the first main branch hole forward branching, and continue drilling the top and bottom secondary branch holes; Step 3: The measuring probe is used to measure the borehole trajectory information, which is recorded and stored by the drilling rig's explosion-proof computer. During the drilling process, the backfill situation is monitored to determine changes in lithology and record them in a timely manner. Step 4: The first branch hole should be used to initially investigate the condition of the top and bottom of the target coal seam. If the actual drilling results show a large discrepancy with the initial geological model, the design of subsequent main holes and branch holes should be adjusted in a timely manner based on the actual drilling results. Step 5: After completing the construction of the first branch hole, pull the drill bit back to the main hole and continue the construction of the main hole and subsequent branch holes; Step Six: After completing all branch drilling operations, lift the drill and retrieve the stored data measured inside the hole; Step 7: Adjust the design of the remaining boreholes based on the construction data of the first borehole, and repeat steps 1 to 6 to complete the construction of the remaining designed boreholes. Then extract the drilling data of each borehole. Step 3: Obtain the lithological stratification curve based on the drilling data. Combine the lithological stratification curve with the borehole trajectory to obtain the target layer top and bottom interface dataset. Step 4: Based on the layering, extract the location of structures on the actual drilling trajectory of each borehole and correct the initial geological model of the working face. Combine the corrected structures in the target layer to form a dataset of structures. Step 5: Draw the three-dimensional spatial distribution based on the target layer top and bottom interface dataset and the constructed dataset.

2. The method for constructing a transparent working face in a fractured and soft coal seam based on directional comb-shaped holes in the bottom plate according to claim 1, characterized in that, To meet the requirements of gas extraction, the spacing between main boreholes should be controlled between 5 and 10 meters. The main boreholes should be constructed using a forward branching method. When designing the trajectory, branch points should be reserved at certain intervals, and the spacing between branch points should not be greater than the extension distance of the branch borehole in the coal seam.

3. The method for constructing a transparent working face in a fractured and soft coal seam based on directional comb-shaped holes in the bottom plate according to claim 1 or 2, characterized in that, When the coal seam thickness is greater than 5m and the difference in coal and rock properties along the coal seam thickness direction (f coefficient) exceeds 0.3, the branch holes should be arranged on the side with better hole formation stability. The number of secondary branch holes is the ratio of the maximum extension distance of the branch holes to the spacing between the secondary branch holes.

4. The method for constructing a transparent working face in a fractured and soft coal seam based on directional comb-shaped holes in the bottom plate according to claim 1 or 2, characterized in that, When the permeability of the coal seam to be extracted is extremely poor, resulting in a borehole extraction influence radius of less than 3m, and there is still a extraction coverage blind zone even with a main borehole spacing of 5m, the first top-exploring secondary branch borehole after entering the coal seam should be arranged slightly to the left or right along the borehole trajectory, and the next top-exploring secondary branch borehole should be arranged accordingly to the right or left. Similarly, bottom-exploring branch boreholes should be arranged. The spacing between the boreholes should be 2 to 3m and should not exceed the extraction influence range. At the same time, the secondary branch boreholes on the left and right sides should be able to overlap to avoid exploration and extraction blind zones in the direction of advancement.

5. The method for constructing a transparent working face in a fractured and soft coal seam based on directional comb-shaped holes in the bottom plate according to claim 1 or 2, characterized in that, Step 3, obtaining the lithological stratification curve based on drilling data, includes: The boundary points of the target layer on the borehole trajectory are extracted to form a top and bottom interface boundary point dataset. Then, the layered dataset is processed, the boundary points of each layer are connected, and a lithological stratification curve is established.

6. The method for constructing a transparent working face in a fractured and soft coal seam based on directional comb-shaped holes in the bottom plate according to claim 5, characterized in that, The processing method of the layered dataset is as follows: the target layer is divided into grids along the vertical plane of the layer height, which determines the x and y coordinates of each grid point. The z coordinate data of the top and bottom interfaces of each grid point are calculated by interpolation of its three nearest measured points. The distance between adjacent grid points is 2 to 3 m.

7. The method for constructing a transparent working face in a fractured and soft coal seam based on directional comb-shaped holes in the bottom plate according to claim 6, characterized in that, Top plate grid points For example, grid points Shaft top plate coordinates The interpolation calculation method is as follows: the coordinates of its three nearest adjacent actual exposed roof interface points are... , The direction vectors of the two points , Use respectively , Instead, the normal vectors of the three points are coplanar. Then, based on the plane normal vector Grid points on the plane The point-normal form of the plane equation is: Finally, based on the desired point , Values, substitute into the formula to solve The value is sufficient; Similarly, the coordinates of its three nearest adjacent actual exposed base plate interface points are: , , Then the base plate grid points base plate Shaft base plate coordinates The interpolation calculation method is based on the direction vectors of the two points. , Use respectively , Instead, the normal vectors of the three points are coplanar. Then, based on the plane normal vector Grid points on the plane The point-normal form of the plane equation is: Finally, based on the desired point , Values, substitute into the formula to solve The value is sufficient; The target layer top and bottom interface dataset is obtained through the above data processing.

8. The method for constructing a transparent working face in a fractured and soft coal seam based on directional comb-shaped holes in the bottom plate according to claim 1 or 2, characterized in that, Step 4 specifically includes: accurate exploration of known structures, identification of unknown structures encountered during drilling and extraction of the location of structures on each borehole trajectory, and combination of known and unknown structures within the target layer to form a dataset of structures.

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