Intelligent identification method for gas enrichment area based on block discrete element-finite element combined modeling

Abstract

The invention discloses an intelligent identification method for a gas enrichment area based on block discrete element-finite element combined modeling. The method comprises the following steps: collecting rock stratum geological data and mine production data of an abandoned mining area; rock stratum mechanical parameters and gas occurrence parameters are obtained; establishing an equal-proportion three-dimensional mine geologic model in the block discrete element UDEC; carrying out excavation and balance simulation on a recovery section, and extracting a stope crack image after excavation; the stope fracture image is imported into image recognition software Coreldraw, and the coordinate of each stope fracture is obtained; establishing a space grid model in MATLAB, and endowing permeability by utilizing a mutual relation between coordinates of the stope fracture and a space grid; and importing the obtained permeability into finite element software COMSOL in the form of an interpolation method to perform gas flow simulation, and performing comprehensive judgment on gas emission and enrichment areas. According to the method, the gas enrichment area under the abandoned mining field can be accurately determined, and scientific guidance can be provided for arrangement of the gas extraction well on the ground.

Description

Technical Field

[0001] The present invention belongs to the technical field of intelligent identification, and in particular relates to an intelligent identification method for gas-rich areas by block discrete element-finite element joint modeling. Background Art

[0002] With the adjustment of China's energy structure, coal mining has developed from the original decentralized mining to refined, centralized and precise mining. At present, the number of mines has been greatly reduced, and a large number of mines with depleted resources and backward production capacity are facing closure or abandonment. It is estimated that the number of abandoned mines will reach about 15,000 by 2030. After a lot of exploration and research, it is preliminarily estimated that there are still nearly 500 billion m3 of unconventional natural gas in closed / abandoned mines. 3 . Gas is a clean and efficient energy source, which is widely used in heating, cooking, power generation and other fields. The heat energy generated by gas combustion can be converted into electrical energy, providing convenience for people's lives and work. At the same time, gas is a very dangerous gas, which not only causes explosions, but also causes air pollution. If systematic and standardized mining and management operations are not carried out, it will have a huge impact on the environment. At the same time, there will be great safety risks. In 2019, the proportion of methane emissions from abandoned mines in my country has reached 15%, and its proportion will continue to increase with the development of production and the needs of life. Since a large amount of gas accumulates in the goaf, gas explosion accidents are very likely to occur, which poses a serious threat to the extraction of gas and the scientific management of abandoned mining areas. Therefore, carrying out gas extraction and management operations in abandoned mines has very important economic, environmental and safety benefits.

[0003] At present, in order to ensure the safe and efficient gas extraction operations, it is very necessary to carry out research on gas extraction in abandoned mines. Through preliminary analysis and research, the gas-enriched areas can be determined, which is conducive to scientifically and rationally guiding the layout of subsequent gas extraction wells. At the same time, it can provide reliable technical support for the subsequent safe extraction of gas. For this reason, it is urgent to provide a new type of intelligent identification method for gas-enriched areas. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for intelligent identification of gas-enriched areas by block discrete element-finite element joint modeling. The method has a simple operation process and low implementation cost. It can accurately determine the underground gas-enriched areas in abandoned mining areas and provide scientific guidance for the layout of ground gas extraction wells.

[0005] In order to achieve the above object, the present invention provides a method for intelligently identifying gas-rich areas by block discrete element-finite element joint modeling, comprising the following steps:

[0006] Step 1: Collect geological data of rock formations and mine production data of abandoned mining areas; construct sampling drills on the surface of the mining area to perform in-situ coring of each coal and rock layer to obtain core samples of each coal and rock, and then obtain the rock formation mechanical parameters and gas occurrence parameters of each coal and rock core sample through laboratory testing;

[0007] Step 2: Establish a proportional three-dimensional mine geological model in the block discrete element UDEC according to the rock geological data, rock mechanical parameters and gas storage parameters. At the same time, set the parameters of the proportional three-dimensional mine geological model and calculate it to the stress equilibrium state;

[0008] Step 3: Based on the collected mine production data, use the proportional three-dimensional mine geological model to simulate the excavation and balance of the mining section; use the built-in jointed-open function of the software to extract the crack image of the mining area after excavation;

[0009] Step 4: Import the obtained stope fissure image into the image recognition software Coreldraw, and use the image recognition software Coreldraw to perform vector processing to obtain the coordinates of each stope fissure;

[0010] Step 5: Establish a spatial grid model in MATLAB and assign permeability using the relationship between the coordinates of the stope fractures and the spatial grid;

[0011] Step 6: Import the obtained permeability into the finite element software COMSOL in the form of interpolation method to simulate the gas flow, and make a comprehensive judgment on the gas outburst and enrichment areas, and finally obtain the abandoned mine gas enrichment area.

[0012] As a preferred embodiment, in S11 of step 2, the parameters of the proportional three-dimensional mine geological model include deadweight and boundary conditions.

[0013] As a preferred embodiment, in step one, the rock stratum geological data include coal rock stratum distribution, coal seam inclination, and coal seam direction; the mine production data include coal mining volume, production and abandonment years information of the mining area; and the gas occurrence parameters include permeability, gas content, and gas pressure.

[0014] As a preferred embodiment, in step 4, before importing the stope fissure image into the image recognition software Coreldraw, the stope fissure image is firstly binarized.

[0015] Furthermore, in order to accurately and efficiently distribute the permeability of the stope fractures, in step 5, the process of establishing a spatial grid model and assigning permeability is as follows:

[0016] S51: Extract the spatial coordinates of the cracks and establish an i*4 crack coordinate matrix F in MATLAB, as shown in formula (1);

[0017]

[0018] Where i is the crack number obtained; x i1 、x i2 are the x coordinates of the two ends of the crack; y i1 ,y i2 are the y coordinates of the two ends of the crack;

[0019] S52: Establish a space of the same size as the proportional three-dimensional mine geological model in MATLAB, and grid the space to divide it into 1j 20*20 cm grids; obtain the coordinates of the four endpoints of each grid and establish a j*9 matrix G, as shown in formula (2);

[0020]

[0021] Where j is the obtained grid number; x i1 、x i2 、x i3 、x i4 are the x coordinates of the four endpoints of the grid; y i1 ,y i2 ,y i3 ,y i4 are the y coordinates of the four endpoints of the grid respectively; the first column in the matrix is ​​the permeability of the grid, and the initial permeability of the grid is uniformly set to 0;

[0022] S53: Using MATLAB, determine the grid interval where each crack is located, and perform cyclic determination on the inclination angle of the crack. The specific process is as follows:

[0023] A1: If the x coordinates x at both ends of the current crack i i1 、x i2 The minimum value of is less than the x coordinates x of the four endpoints of the jth network j1 、x j2 、x j3 、x j4 The maximum value of the current crack i, and the x coordinates x at both ends of the crack i i1 、x i2 The maximum value of is greater than the x coordinates x of the four endpoints of the jth network j1 、x j2 、x j3 、x j4 If the minimum value of is reached, the judgment condition is met and A2 is executed. Otherwise, the judgment condition is not met, so let j=j+1 and re-execute A1 until the judgment condition is met.

[0024] A2: If the y coordinates y at both ends of the current crack i i1 ,y i2The minimum value of is less than the y coordinates y of the four endpoints of the jth network j1 ,y j2 ,y j3 ,y j4 The maximum value of the current crack i, and the y coordinates y at both ends of the crack i i1 ,y i2 The maximum value of is greater than the y coordinates y of the four endpoints of the jth network j1 ,y j2 ,y j3 ,y j4 If the minimum value is reached, the judgment condition is met and A3 is executed. Otherwise, the judgment condition is not met, so let j=j+1 and re-execute A2 until the judgment condition is met.

[0025] A3: Based on the obvious difference in permeability of fractures with different inclination angles, the inclination angle of the fracture is determined as follows;

[0026] The grids with fracture dip angle greater than 45° are assigned permeability k1, the grids with fracture dip angle less than or equal to 45° are assigned permeability k2, and the items in the matrix G(j,1) that are still 0 are assigned permeability k3, as shown in formula (3);

[0027]

[0028] A4: Let i=i+1, and repeat A1 to A3;

[0029] A5: Repeat A4 several times until the allocation of all fracture permeabilities is completed, and finally the permeability within the spatial grid is obtained.

[0030] In the present invention, a sampling drill is used to drill core samples in the mining area, and then the core samples are placed in the laboratory for testing, so that accurate rock stratum mechanical parameters and gas storage parameters can be obtained. In this way, by combining the rock stratum mechanical parameters, gas storage parameters and the rock stratum geological data collected in the early stage, a proportional three-dimensional mine geological model that is highly consistent with the actual environment can be easily established using the block discrete element UDEC, providing a reliable technical guarantee for obtaining accurate analysis results in the future. By performing excavation and balance simulation of the mining section on the proportional three-dimensional mine geological model, working conditions that are consistent with the actual environment can be efficiently and accurately simulated under the premise of effectively reducing the material and human resource cost investment. First, the built-in jointed-open function of the software is used to extract the image of the cracks in the mining area after excavation, and then the image recognition software Coreldraw is used to obtain the coordinates of each crack. Then, MATLAB is used to establish a spatial grid model, and the permeability is assigned based on the correlation between the coordinates of the cracks in the mining area and the spatial grid. This can efficiently and accurately assign permeabilities that are consistent with the actual environment to the cracks in different parts of the constructed proportional three-dimensional mining geological model, which can help to intuitively and accurately determine the effective migration channels of gas. At the same time, it can also facilitate the determination of the potential migration path of gas through analysis. In this way, through the gas flow simulation method of the finite element software COMSOL, the migration channel and the potential migration path can be effectively combined, so that the gas enrichment area can be accurately determined, and then the layout of the ground gas extraction wells can be reasonably guided. At the same time, it can provide reliable technical support for the subsequent safe and efficient extraction of gas.

[0031] This method has a simple operation process and low implementation cost. It effectively combines the advantages of block discrete element and finite element simulation, can accurately determine the underground gas enrichment area of ​​abandoned mines, and can provide scientific guidance for the layout of ground gas extraction wells. At the same time, it can be convenient to form a visual terminal with the help of COMSOL software app developer, which is conducive to the real-time guidance of the precise mining process of abandoned mine gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart of the present invention;

[0033] Figure 2 is a flow chart of the process of allocating the permeability of the stope fractures in the present invention;

[0034] Figure 3 It is a schematic diagram of the process of vectorization and spatial gridding of mining fractures in the present invention;

[0035] Figure 4 It is a distribution characteristic diagram of the gas-enriched area of ​​the stope in the present invention;

[0036] Figure 5 It is a diagram of gas emission rules in the mining area of ​​the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with the embodiments.

[0038] like Figure 1 As shown, the present invention provides a method for intelligently identifying gas-rich areas by block discrete element-finite element joint modeling, comprising the following steps:

[0039] Step 1: Collect geological data of rock formations and mine production data of abandoned mining areas; construct sampling drills on the surface of the mining area to perform in-situ coring of each coal and rock layer to obtain core samples of each coal and rock, and then obtain the rock formation mechanical parameters and gas occurrence parameters of each coal and rock core sample through laboratory testing;

[0040] Step 2: Establish a proportional three-dimensional mine geological model in the block discrete element UDEC according to the rock geological data, rock mechanical parameters, and gas storage parameters. At the same time, set the parameters of the proportional three-dimensional mine geological model and calculate it to a stress equilibrium state;

[0041] Step 3: Based on the collected mine production data, use the proportional three-dimensional mine geological model to simulate the excavation and balance of the mining section; use the built-in jointed-open function of the software to extract the crack image of the mining area after excavation;

[0042] Step 4: Import the obtained stope fissure image into the image recognition software Coreldraw, and use the image recognition software Coreldraw to perform vector processing to obtain the coordinates of each stope fissure;

[0043] Step 5: Establish a spatial grid model in MATLAB and assign permeability using the relationship between the coordinates of the stope fractures and the spatial grid;

[0044] like Figure 3 As shown, it shows the schematic diagram of the vectorization and spatial gridding process of mining fractures;

[0045] Step 6: Import the obtained permeability into the finite element software COMSOL in the form of interpolation method to simulate the gas flow, and make a comprehensive judgment on the gas outburst and enrichment areas, and finally obtain the abandoned mine gas enrichment area.

[0046] like Figure 4 As shown in Figure 1, it shows the distribution characteristics of the gas-rich area in the mining area; Figure 5 As shown, it shows the regularity of gas emission in the mining area;

[0047] As a preferred embodiment, in S11 of step 2, the parameters of the proportional three-dimensional mine geological model include deadweight and boundary conditions.

[0048] As a preferred embodiment, in step one, the rock stratum geological data include coal rock stratum distribution, coal seam inclination, and coal seam direction; the mine production data include coal mining volume, production and abandonment years information of the mining area; and the gas occurrence parameters include permeability, gas content, and gas pressure.

[0049] As a preferred embodiment, in step 4, before importing the stope fissure image into the image recognition software Coreldraw, the stope fissure image is firstly binarized.

[0050] like Figure 2 As shown in the figure, in order to accurately and efficiently distribute the permeability of the stope fractures, in step five, the process of establishing the spatial grid model and assigning the permeability is as follows:

[0051] S51: Extract the spatial coordinates of the cracks and establish an i*4 crack coordinate matrix F in MATLAB, as shown in formula (1);

[0052]

[0053] Where i is the crack number obtained; x i1 、x i2 are the x coordinates of the two ends of the crack; y i1 ,y i2 are the y coordinates of the two ends of the crack;

[0054] S52: Establish a space of the same size as the proportional three-dimensional mine geological model in MATLAB, and grid the space to divide it into 1j 20*20 cm grids; obtain the coordinates of the four endpoints of each grid and establish a j*9 matrix G, as shown in formula (2);

[0055]

[0056] Where j is the obtained grid number; x i1 、x i2 、x i3 、x i4 are the x coordinates of the four endpoints of the grid; y i1 ,y i2 ,y i3 ,y i4 are the y coordinates of the four endpoints of the grid respectively; the first column in the matrix is ​​the permeability of the grid, and the initial permeability of the grid is uniformly set to 0;

[0057] S53: Using MATLAB, determine the grid interval where each crack is located, and perform cyclic determination on the inclination angle of the crack. The specific process is as follows:

[0058] A1: If the x coordinates x at both ends of the current crack i i1、x i2 The minimum value of is less than the x coordinates x of the four endpoints of the jth network j1 、x j2 、x j3 、x j4 The maximum value of the current crack i, and the x coordinates x at both ends of the crack i i1 、x i2 The maximum value of is greater than the x coordinates x of the four endpoints of the jth network j1 、x j2 、x j3 、x j4 If the minimum value of is reached, the judgment condition is met and A2 is executed. Otherwise, the judgment condition is not met, so let j=j+1 and re-execute A1 until the judgment condition is met.

[0059] A2: If the y coordinates y at both ends of the current crack i i1 ,y i2 The minimum value of is less than the y coordinates y of the four endpoints of the jth network j1 ,y j2 ,y j3 ,y j4 The maximum value of the current crack i, and the y coordinates y at both ends of the crack i i1 ,y i2 The maximum value of is greater than the y coordinates y of the four endpoints of the jth network j1 ,y j2 ,y j3 ,y j4 If the minimum value is reached, the judgment condition is met and A3 is executed. Otherwise, the judgment condition is not met, so let j=j+1 and re-execute A2 until the judgment condition is met.

[0060] A3: Based on the obvious difference in permeability of fractures with different inclination angles, the inclination angle of the fracture is determined as follows;

[0061] The grids with fracture dip angle greater than 45° are assigned permeability k1, the grids with fracture dip angle less than or equal to 45° are assigned permeability k2, and the items in the matrix G(j,1) that are still 0 are assigned permeability k3, as shown in formula (3);

[0062]

[0063] A4: Let i=i+1, and repeat A1 to A3;

[0064] A5: Repeat A4 several times until the allocation of all fracture permeabilities is completed, and finally the permeability within the spatial grid is obtained.

[0065] In the present invention, a sampling drill is used to drill core samples in the mining area, and then the core samples are placed in the laboratory for testing, so that accurate rock stratum mechanical parameters and gas storage parameters can be obtained. In this way, by combining the rock stratum mechanical parameters, gas storage parameters and the rock stratum geological data collected in the early stage, a proportional three-dimensional mine geological model that is highly consistent with the actual environment can be easily established using the block discrete element UDEC, providing a reliable technical guarantee for obtaining accurate analysis results in the future. By performing excavation and balance simulation of the mining section on the proportional three-dimensional mine geological model, working conditions that are consistent with the actual environment can be efficiently and accurately simulated under the premise of effectively reducing the material and human resource cost investment. First, the built-in jointed-open function of the software is used to extract the image of the cracks in the mining area after excavation, and then the image recognition software Coreldraw is used to obtain the coordinates of each crack. Then, MATLAB is used to establish a spatial grid model, and the permeability is assigned based on the correlation between the coordinates of the cracks in the mining area and the spatial grid. This can efficiently and accurately assign permeabilities that are consistent with the actual environment to the cracks in different parts of the constructed proportional three-dimensional mining geological model, which can help to intuitively and accurately determine the effective migration channels of gas. At the same time, it can also facilitate the determination of the potential migration path of gas through analysis. In this way, through the gas flow simulation method of the finite element software COMSOL, the migration channel and the potential migration path can be effectively combined, so that the gas enrichment area can be accurately determined, and then the layout of the ground gas extraction wells can be reasonably guided. At the same time, it can provide reliable technical support for the subsequent safe and efficient extraction of gas.

[0066] This method has a simple operation process and low implementation cost. It effectively combines the advantages of block discrete element and finite element simulation, can accurately determine the underground gas enrichment area of ​​abandoned mines, and can provide scientific guidance for the layout of ground gas extraction wells. At the same time, it can be convenient to form a visual terminal with the help of COMSOL software app developer, which is conducive to the real-time guidance of the precise mining process of abandoned mine gas.

Claims

1. A method for intelligent identification of gas-rich areas based on block discrete element-finite element joint modeling, characterized in that: The following steps are involved: Step 1: Collect geological data of rock formations and mine production data of abandoned mining areas; construct sampling drills on the surface of the mining area to perform in-situ coring of each coal and rock layer to obtain core samples of each coal and rock, and then obtain the rock formation mechanical parameters and gas occurrence parameters of each coal and rock core sample through laboratory testing; Step 2: Establish a proportional three-dimensional mine geological model in the block discrete element UDEC according to the rock geological data, rock mechanical parameters and gas storage parameters. At the same time, set the parameters of the proportional three-dimensional mine geological model and calculate it to the stress equilibrium state; Step 3: Based on the collected mine production data, use the proportional three-dimensional mine geological model to simulate the excavation and balance of the mining section; use the built-in jointed-open function of the software to extract the crack image of the mining area after excavation; Step 4: Import the obtained stope fissure image into the image recognition software Coreldraw, and use the image recognition software Coreldraw to perform vector processing to obtain the coordinates of each stope fissure; Step 5: Establish a spatial grid model in MATLAB and assign permeability using the relationship between the coordinates of the stope fractures and the spatial grid; Step 6: Import the obtained permeability into the finite element software COMSOL in the form of interpolation method to simulate the gas flow, and make a comprehensive judgment on the gas outburst and enrichment areas, and finally obtain the abandoned mine gas enrichment area.

2. According to claim 1, a method for intelligent identification of gas-rich areas by block discrete element-finite element joint modeling is characterized in that: In step S11 of step 2, the parameters of the proportional three-dimensional mine geological model include deadweight and boundary conditions.

3. The intelligent identification method of gas-rich areas by block discrete element-finite element joint modeling according to claim 1 or 2 is characterized in that: In step one, the rock geological data include coal rock layer distribution, coal seam inclination, coal seam direction, the mine production data include mining area coal production, production and abandonment years information, the gas storage parameters include permeability, gas content, gas pressure.

4. The intelligent identification method of gas-rich areas by block discrete element-finite element joint modeling according to claim 3 is characterized in that: In step 4, before importing the stope fissure image into the image recognition software Coreldraw, the stope fissure image is firstly binarized.

5. The intelligent identification method of gas-rich areas by block discrete element-finite element joint modeling according to claim 4 is characterized in that: In step 5, the process of establishing a spatial grid model and assigning permeability is as follows: S51: Extract the spatial coordinates of the cracks and establish an i*4 crack coordinate matrix F in MATLAB, as shown in formula (1); Where i is the crack number obtained; x i1 、x i2 are the x coordinates of the two ends of the crack; y i1 ,y i2 are the y coordinates of the two ends of the crack; S52: Establish a space of the same size as the proportional three-dimensional mine geological model in MATLAB, and grid the space to divide it into 1j 20*20 cm grids; obtain the coordinates of the four endpoints of each grid and establish a j*9 matrix G, as shown in formula (2); Where j is the obtained grid number; x i1 、x i2 、x i3 、x i4 are the x coordinates of the four endpoints of the grid; y i1 ,y i2 ,y i3 ,y i4 are the y coordinates of the four endpoints of the grid respectively; the first column in the matrix is ​​the permeability of the grid, and the initial permeability of the grid is uniformly set to 0; S53: Using MATLAB, determine the grid interval where each crack is located, and perform cyclic determination on the inclination angle of the crack. The specific process is as follows: A1: If the x coordinates x at both ends of the current crack i i1 、x i2 The minimum value of is less than the x coordinates x of the four endpoints of the jth network j1 、x j2 、x j3 、x j4 The maximum value of the current crack i, and the x coordinates x at both ends of the crack i i1 、x i2 The maximum value of is greater than the x coordinates x of the four endpoints of the jth network j1 、x j2 、x j3 、x j4 If the minimum value of is reached, the judgment condition is met and A2 is executed. Otherwise, the judgment condition is not met, so let j=j+1 and re-execute A1 until the judgment condition is met. A2: If the y coordinates y at both ends of the current crack i i1 ,y i2 The minimum value of is less than the y coordinates y of the four endpoints of the jth network j1 ,y j2 ,y j3 ,y j4 The maximum value of the current crack i, and the y coordinates y at both ends of the crack i i1 ,y i2 The maximum value of is greater than the y coordinates y of the four endpoints of the jth network j1 ,y j2 ,y j3 ,y j4 If the minimum value is reached, the judgment condition is met and A3 is executed. Otherwise, the judgment condition is not met, so let j=j+1 and re-execute A2 until the judgment condition is met. A3: Based on the obvious difference in permeability of fractures with different inclination angles, the inclination angle of the fracture is determined as follows; The grids with fracture dip angle greater than 45° are assigned permeability k1, the grids with fracture dip angle less than or equal to 45° are assigned permeability k2, and the items in the matrix G(j,1) that are still 0 are assigned permeability k3, as shown in formula (3); A4: Let i=i+1, and repeat A1 to A3; A5: Repeat A4 several times until the allocation of all fracture permeabilities is completed, and finally the permeability within the spatial grid is obtained.

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