Coal seam gas extraction intelligent evaluation method

Abstract

The application discloses a coal seam gas extraction intelligent evaluation method, in the coal seam gas flow field monitoring process, the gas flow in the extraction pipeline is monitored in real time through the construction of the through-hole drilling; in the accurate inversion process of the coal seam gas flow parameter, the target error function between the measured gas flow and the model gas flow is constructed based on the radial coal seam unstable flow theory, and the coal seam gas flow parameter closest to the real coal seam numerical value is accurately inverted by using the coordinate alternation method; in the intelligent evaluation process of the coal seam gas outburst elimination, the coal seam gas extraction numerical model is established by using the obtained coal seam gas flow parameter, and the intelligent evaluation on the outburst elimination condition of the coal seam is carried out based on the calculated residual gas pressure and residual gas content, so that the problems of low evaluation result precision of the extraction monitoring data, many artificial subjective factors and the like at the present stage are overcome, guidance for the determination of the extraction drilling spacing and the extraction standard time length is provided, and finally strong technical support for reducing the coal seam gas outburst risk is provided.

Description

Technical Field

[0001] This invention relates to an intelligent evaluation method for coal seam gas extraction, belonging to the field of mine gas extraction technology. Background Technology

[0002] With the continuous development and iteration of underground mining technology and equipment, the mining intensity and depth of mines will be further increased, the coal seam gas content and ground stress will increase sharply, the gas emission and the risk of coal and gas outbursts will increase significantly, and because coal and gas outbursts are highly concealed, they pose a serious threat to safe underground mining.

[0003] Gas drainage is the fundamental solution to coal mine gas disasters and a key technology for solving the problem of deep gas disaster prevention and control and improving the level of coal mine safety production. Effectively identifying coal and gas outburst hazards is also an important task in gas disaster prevention and control. Currently, the main methods for identifying coal and gas outburst hazards include geophysical exploration and measurement while drilling (MWD). Geophysical exploration has the advantages of rich response information, rapid construction, and wide detection area, but it has the disadvantages of multiple solutions and low accuracy. MWD has the advantages of strong intuitiveness and high testing accuracy, but it has the disadvantages of overgeneralization and small detection area. Therefore, how to balance gas control engineering and detection engineering is currently the top priority in coal mine gas disaster management.

[0004] Currently, to curb coal and gas outburst disasters, a large number of cross-seam boreholes need to be constructed. The existence of these boreholes provides a solid material foundation for drilling technology. However, the drilling data during the construction of these boreholes has not been effectively collected, and the collected data lacks a reliable inversion model to convert the tested electrical signals into coal seam gas flow characteristic parameters. This results in low accuracy and a large number of subjective human factors in the current evaluation results of extraction monitoring data. Furthermore, it is currently impossible to provide guidance on how to determine a better borehole construction plan for unextracted coal seams. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an intelligent evaluation method for coal seam gas drainage. This method efficiently utilizes drilling information from regional gas control projects, constructs a target error function between measured gas flow and model gas flow based on radial coal seam unsteady flow theory, and accurately derives the initial gas pressure and permeability coefficient of the coal seam using the coordinate rotation method. This intelligently evaluates the coal seam gas outburst mitigation status, overcoming the current problems of low accuracy and numerous subjective human factors in the evaluation results of drainage monitoring data. Furthermore, it provides guidance for determining the spacing between drainage boreholes and the duration of drainage compliance.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: an intelligent evaluation method for coal seam gas extraction, the specific steps of which are as follows:

[0007] Step 1: On-site monitoring of coal seam gas flow:

[0008] S1. Construct cross-layer drilling according to the needs of regional gas control projects, and record the construction parameters of cross-layer drilling during construction (i.e., collect drilling information).

[0009] S2. Lay the gas extraction pipeline into the cross-layer borehole, and then seal the cross-layer borehole.

[0010] S3. Install a flow meter on one of the gas extraction pipelines in the cross-layer borehole, and connect the flow meter to the ground monitoring center through a monitoring instrument, a downhole monitoring substation and a downhole ring network, so as to realize real-time monitoring of the gas flow rate in the extraction pipeline;

[0011] S4. Obtain coal samples from the target coal seam on-site and measure the samples in the laboratory to obtain the Langmuir adsorption constants a and b, and the coal porosity of the target coal seam. Given the apparent density ρ, since the gas content W per unit volume of coal can be expressed by both the Langmuir equation and an approximate parabolic equation, the coal seam gas content coefficient α is fitted using the Langmuir adsorption curve equation. The fitting formula is:

[0012]

[0013] Wherein, W represents the methane content per unit volume of coal; a and b represent Langmuir adsorption constants. - Coal porosity; p - Coal seam gas pressure; B - Unit conversion coefficient; ρ - Apparent density of coal; α - Coal seam gas content coefficient;

[0014] S5. After the flow meter's flow count stabilizes, the test of the cross-layer borehole is ended, and the corresponding coal seam gas content coefficient α is obtained.

[0015] S6. After completing the previous borehole test, install the flow meter onto the extraction pipeline of the next borehole to be tested.

[0016] Step 2: Accurate inversion of coal seam gas flow parameters:

[0017] I. Using the theory of radial flow of gas in coal seams, a radially unsteady flow flow model of gas in coal seams is constructed, and the flow equation for the radially unsteady flow field in finite coal seams is obtained as follows:

[0018]

[0019]

[0020] Where q is the gas emission per unit area; Y is the dimensionless flow rate; F0 is the dimensionless time rate; λ is the coal seam permeability coefficient; p0 is the initial gas pressure in the coal seam; p1 is the gas pressure in the borehole, which is 0.1 MPa when the atmosphere is vented; R1 is the borehole radius; α is the coal seam gas content coefficient; and t is the time.

[0021] II. Based on the relationship curve between the flow rate number and the time number, the dimensionless equation for radially unsteady flow in a finite coal seam is obtained as follows:

[0022]

[0023] Where Y is the dimensionless flow rate; F0 is the dimensionless time rate;

[0024] III. Construct the objective error function between the measured gas flow rate and the model gas flow rate. The objective error function is:

[0025]

[0026] Where ε is the error precision value. - Actual measured flow rate value - The model calculates the flow rate;

[0027] IV. The coal seam gas flow parameters closest to the true value of the coal seam are obtained by inverting the coordinate rotation method;

[0028] Step 3: Intelligent Evaluation of Coal Seam Gas Outburst Mitigation:

[0029] ① Based on the coal seam gas flow parameters determined in step two;

[0030] ② Based on the finite volume method, a fine numerical model for coal seam gas extraction is established using simulation software. The model is divided into grids, and data on coal seam permeability coefficient, initial coal seam gas pressure, coal seam gas content coefficient, borehole radius, borehole thickness through coal seam, and borehole time are input. The forward model is then used to calculate the coal seam gas flow state.

[0031] ③ Evaluate the outburst mitigation status of the coal seam based on the residual gas pressure and residual gas content calculated by simulation software. If the simulation results show that the residual gas pressure is <0.74 MPa and the residual gas content is <6.0 m³ / s, the outburst mitigation status is considered. 3 If the value is / t, the gas outburst suppression of the coal seam area is considered to meet the standard; otherwise, it does not meet the standard, and the outburst suppression evaluation of the extracted coal seam is completed.

[0032] ④ Based on the actual conditions of the unextracted coal seam, pre-set different combinations of borehole radius, borehole spacing, and number of boreholes. Repeat step ② to establish a detailed numerical model of coal seam gas drainage under different combinations. Then, evaluate the outburst reduction status of different combinations through step ③ to select the combination that meets the gas outburst reduction standard for the unextracted coal seam. Among the selected combinations, select the one with the shortest drainage time as the optimal solution. The optimal solution will provide guidance for determining the actual drainage borehole spacing and drainage time for the subsequent extraction of the coal seam.

[0033] Furthermore, the construction parameters for the cross-seam drilling include the construction angle, drilling radius, length of coal seam penetration, and drilling time.

[0034] Furthermore, the sealing process employs a "two-plug-one-injection" pressurized sealing method.

[0035] Furthermore, the coal seam gas flow parameters include the initial gas pressure of the coal seam and the coal seam permeability coefficient.

[0036] Furthermore, the specific process of using the coordinate rotation method in step IV to derive the initial gas pressure and permeability coefficient of the coal seam that are closest to the true values ​​of the coal seam is as follows:

[0037] i. Determine the initial values ​​of the initial gas pressure p0 and the coal seam permeability coefficient λ as the initial point X0 for iteration. (0) ;

[0038] ii. At this point, keeping the coal seam permeability coefficient λ constant, a one-dimensional search is performed along the direction of the initial gas pressure p0. Before the search, the direction of descent of the target error function value is determined using a trial-and-error method, denoted as e1, thereby determining the optimal step size α1. At this point, the first iteration point X1 of the first round can be obtained. (1) =X0 (0) +α1 (1) e1;

[0039] iii. Using X1 (1) Starting from this point, keeping the initial gas pressure p0 of the coal seam constant, a one-dimensional search is performed along the direction of the coal seam permeability coefficient. Before the search, the direction of descent of the target error function value is determined using the trial-and-error method, denoted as e2, thus determining the optimal step size α2. At this point, the second iteration point X2 of the first round can be obtained. (1) =X1 (1) +α2 (1) e2, at this point the initial gas pressure p0 and the permeability coefficient λ of the coal seam have completed the first iteration through two one-dimensional searches;

[0040] iv. Continue iterating in the same way as above. As the iteration progresses, the target error function value decreases continuously. When the error accuracy value of the target error function is ≤1e-5, that is, when the accuracy requirement is met, the calculation ends. At this time, it means that the initial gas pressure and permeability coefficient of the coal seam have been inverted to be closest to the true value of the coal seam.

[0041] Furthermore, the simulation software is COMSOL simulation software.

[0042] Furthermore, the initial values ​​of the initial gas pressure and the initial permeability coefficient of the coal seam are determined based on the actual occurrence of gas in the coal seam.

[0043] Compared with existing technologies, this invention comprises three sub-steps: on-site monitoring of coal seam gas flow, accurate inversion of coal seam gas flow parameters, and intelligent evaluation of coal seam gas outburst mitigation. In the on-site monitoring of coal seam gas flow, real-time monitoring of gas flow within the underground extraction pipeline is achieved through drilling across the coal seam, and the coal seam gas content coefficient is derived by fitting the data. In the accurate inversion of coal seam gas flow parameters, a target error function between the measured gas flow and the model gas flow is constructed based on the radial coal seam unsteady flow theory. The coordinate transformation method is then used to accurately invert the coal seam gas flow parameters that most closely approximate the actual coal seam values. These parameters include the coal seam permeability coefficient and the initial coal seam gas pressure. In the intelligent evaluation of coal seam gas outburst mitigation, the coal seam gas flow parameters obtained through inversion can be used to establish a numerical model for coal seam gas drainage. Based on the calculated residual gas pressure and residual gas content, the outburst mitigation status of the coal seam can be intelligently evaluated. If the evaluation meets the standards, it indicates that the drained coal seam can proceed with subsequent mining operations. If it does not meet the standards, the gas drilling construction plan needs to be adjusted to continue gas drainage until the standards are met. Furthermore, this invention can set different drainage plans according to the actual situation of the un-drained coal seam, simulate and evaluate different drainage plans, screen out the plan that can achieve the gas drainage standard, and select the plan with the shortest drainage standard achievement time as the optimal plan. As can be seen from the above process, this invention can efficiently utilize drilling information in regional gas control projects to accurately deduce the initial gas pressure and permeability coefficient of the coal seam, thereby intelligently evaluating the gas outburst mitigation status of the coal seam. It overcomes the problems of low accuracy of current extraction monitoring data evaluation results and many subjective human factors. Through the optimal solution, it can provide guidance for determining the spacing of extraction boreholes and the extraction time to meet standards, ultimately providing strong technical support for reducing the risk of coal seam gas outbursts. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the overall process of the present invention;

[0045] Figure 2 This is a schematic diagram of the equipment layout for on-site drilling of through-layers according to the present invention;

[0046] Figure 3 This is a schematic diagram of the equipment layout when the gas flow rate in the extraction pipeline is measured on-site according to the present invention;

[0047] Figure 4 This is a schematic diagram of the inversion process using the coordinate rotation method in this invention;

[0048] Figure 5 This is a schematic diagram illustrating the principle of the coordinate rotation method in this invention.

[0049] In the diagram: 1-rock tunnel, 2-water pump, 3-hydraulic drilling rig, 4-through-layer borehole, 5-entry point into coal seam, 6-passage point through coal seam, 7-coal seam, 8-roof, 9-floor, 10-monitoring instrument, 11-underground monitoring substation, 12-underground ring network, 13-surface monitoring center, 14-grouting pipe, 15-gas extraction pipeline, 16-flow meter, 17-extraction main pipe. Detailed Implementation

[0050] The present invention will be further described below.

[0051] like Figure 1 As shown, the specific steps of this invention are as follows:

[0052] Step 1: On-site monitoring of coal seam gas flow:

[0053] S1. According to the needs of regional gas control project, a hydraulic drilling system is used to construct multiple cross-layer boreholes 4 from rock tunnel 1 to coal seam 7. During construction, the construction parameters of cross-layer boreholes 4 are recorded (i.e., information collected while drilling), including construction angle, borehole radius, length of coal seam penetration and borehole time.

[0054] S2. Lay the gas extraction pipeline 15 into the cross-layer borehole 4, and then seal the cross-layer borehole 4 using the "two plugs and one injection" pressurized sealing method. The specific sealing process is as follows: First, use bagged polyurethane to plug both ends of the sealing section. After the foamed sealing bag expands and solidifies, grout is injected into the borehole section between the two polyurethane plugs through the grouting pipe. Under the action of grouting pressure, the grout penetrates into the borehole wall and fills the cracks around the borehole.

[0055] S3. Install a flow meter 16 on the gas extraction pipeline 15 of the through-hole 4, and connect the gas extraction pipeline 15 to the extraction main pipeline 17. Simultaneously, connect the flow meter 16 to the data transmission system to achieve real-time monitoring of the gas flow rate in the extraction pipeline; Figure 2 and Figure 3As shown, the equipment used for on-site construction of the cross-layer borehole 4 and on-site measurement of gas flow in the extraction pipeline includes a hydraulic drilling system, a flow meter 16, and a data transmission system. The hydraulic drilling system includes a hydraulic drilling rig 3, drill rods, and drill bits connected in sequence within the rock tunnel 1, and a water pump 2 for spraying water onto the drill bit. The flow meter 16 is installed on the extraction pipeline 15 and is used to collect the gas flow in the gas extraction pipeline 15 in real time. The data transmission system includes a monitoring instrument 10, an underground monitoring substation 11, an underground ring network 12, and a surface monitoring center 13. The monitoring instrument 10 receives and processes the gas flow information in the gas extraction pipeline 15 sent in real time by the flow meter 16 and sends the gas flow information in the extraction borehole to the underground monitoring substation 11. The underground monitoring substation 11 uploads the gas flow data to the surface monitoring center 13 through the underground ring network 12. The monitoring instrument 10 is connected to the flow meter 16 and the underground monitoring substation 11 via mining cables.

[0056] S4. Obtain coal samples from the target coal seam on-site and measure the samples in the laboratory to obtain the Langmuir adsorption constants a and b, and the coal porosity of the target coal seam. Given the apparent density ρ, since the gas content W per unit volume of coal can be expressed by both the Langmuir equation and an approximate parabolic equation, the coal seam gas content coefficient α is fitted using the Langmuir adsorption curve equation. The fitting formula is:

[0057]

[0058] Wherein, W represents the methane content per unit volume of coal; a and b represent Langmuir adsorption constants. - Coal porosity; p - Coal seam gas pressure; B - Unit conversion coefficient; ρ - Apparent density of coal; α - Coal seam gas content coefficient;

[0059] S5. After the flow meter count stabilizes, the test of the cross-layer borehole 4 is completed, and the corresponding coal seam gas content coefficient α is obtained.

[0060] S6. After the previous borehole test is completed, install the flow meter on the extraction pipeline of the next borehole to be tested. Steps S1 to S5 can be repeated for each cross-layer borehole to obtain the gas flow rate and coal seam gas content coefficient α corresponding to each cross-layer borehole.

[0061] Step 2: Accurate inversion of coal seam gas flow parameters:

[0062] I. Using the theory of radial flow of gas in coal seams, a radially unsteady flow flow model of gas in coal seams is constructed, and the flow equation for the radially unsteady flow field in finite coal seams is obtained as follows:

[0063]

[0064]

[0065] Where q is the gas emission per unit area; Y is the dimensionless flow rate; F0 is the dimensionless time rate; λ is the coal seam permeability coefficient; p0 is the initial gas pressure in the coal seam; p1 is the gas pressure in the borehole, which is 0.1 MPa when the atmosphere is vented; R1 is the borehole radius; α is the coal seam gas content coefficient; and t is the time.

[0066] II. Based on the relationship curve between the flow rate number and the time number, the dimensionless equation for radially unsteady flow in a finite coal seam is obtained as follows:

[0067]

[0068] Where Y is the dimensionless flow rate; F0 is the dimensionless time rate;

[0069] III. Construct the objective error function between the measured gas flow rate and the model gas flow rate. The objective error function is:

[0070]

[0071] Where ε is the error precision value. - Actual measured flow rate value - The model calculates the flow rate;

[0072] IV. The coal seam gas flow parameters closest to the true values ​​of the coal seam are derived using the coordinate rotation method, including the initial gas pressure and permeability coefficient of the coal seam, such as... Figure 4 and 5 As shown, the specific process is as follows:

[0073] i. Determine the initial values ​​of the initial gas pressure p0 and the coal seam permeability coefficient λ as the initial point X0 for iteration. (0) The initial values ​​for both are generally set as follows: initial gas pressure of the coal seam is 1 MPa, and coal seam permeability coefficient is 0.1 m. 2 / (MPa 2 •d); If the occurrence of coal seam gas is abnormal, it shall be determined according to the actual occurrence of coal seam gas as measured.

[0074] ii. At this point, keeping the coal seam permeability coefficient λ constant, a one-dimensional search is performed along the direction of the initial gas pressure p0. Before the search, the direction of descent of the target error function value is determined using a trial-and-error method, denoted as e1, thereby determining the optimal step size α1. At this point, the first iteration point X1 of the first round can be obtained. (1) =X0 (0) +α1 (1) e1;

[0075] iii. Using X1(1) Starting from this point, keeping the initial gas pressure p0 of the coal seam constant, a one-dimensional search is performed along the direction of the coal seam permeability coefficient. Before the search, the direction of descent of the target error function value is determined using the trial-and-error method, denoted as e2, thus determining the optimal step size α2. At this point, the second iteration point X2 of the first round can be obtained. (1) =X1 (1) +α2 (1) e2, at this point the initial gas pressure p0 and the permeability coefficient λ of the coal seam have completed the first iteration through two one-dimensional searches;

[0076] iv. Continue iterating in the same way as above. As the iteration progresses, the target error function value decreases continuously. When the error accuracy value of the target error function is ≤1e-5, that is, when the accuracy requirement is met, the calculation ends. At this time, it means that the initial gas pressure and permeability coefficient of the coal seam have been inverted to be closest to the true value of the coal seam.

[0077] Step 3: Intelligent Evaluation of Coal Seam Gas Outburst Mitigation:

[0078] ① Based on the coal seam gas flow parameters determined in step two;

[0079] ② Based on the finite volume method, a fine numerical model for coal seam gas extraction was established using COMSOL simulation software. The model was divided into grids, and data on coal seam permeability coefficient, initial coal seam gas pressure, coal seam gas content coefficient, borehole radius, borehole thickness through coal seam, and borehole time were input. The forward model was then used to calculate the coal seam gas flow state.

[0080] ③ Evaluate the coal seam's outburst mitigation status based on the residual gas pressure and residual gas content calculated using COMSOL simulation software. If the simulation results show that the residual gas pressure is <0.74 MPa and the residual gas content is <6.0 m³ / s, the coal seam's outburst mitigation status is considered. 3 If the value is / t, the gas outburst suppression of the coal seam area is considered to meet the standard; otherwise, it does not meet the standard, and the outburst suppression evaluation of the extracted coal seam is completed.

[0081] ④ Based on the actual conditions of the unextracted coal seam, pre-set different combinations of borehole radius, borehole spacing, and number of boreholes. Repeat step ② to establish a detailed numerical model of coal seam gas drainage under different combinations. Then, evaluate the outburst reduction status of different combinations through step ③ to select the combination that meets the gas outburst reduction standard for the unextracted coal seam. Among the selected combinations, select the one with the shortest drainage time as the optimal solution. The optimal solution will provide guidance for determining the actual drainage borehole spacing and drainage time for the subsequent extraction of the coal seam.

[0082] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A smart evaluation method for coal seam gas extraction, characterized in that, The specific steps are as follows: Step 1: On-site monitoring of coal seam gas flow: S1. Construct cross-layer drilling according to the needs of regional gas control projects, and record the construction parameters of cross-layer drilling during construction. S2. Lay the gas extraction pipeline into the cross-layer borehole, and then seal the cross-layer borehole. S3. Install a flow meter on the gas extraction pipeline through the cross-layer borehole, and connect the flow meter to the ground monitoring center through the monitoring instrument, the downhole monitoring substation and the downhole ring network, so as to realize real-time monitoring of the gas flow rate in the extraction pipeline; S4. Obtain coal samples from the target coal seam on-site and measure the samples in the laboratory to obtain the Langmuir adsorption constants a and b, and the coal porosity of the target coal seam. Given the apparent density ρ, since the gas content W per unit volume of coal can be expressed by both the Langmuir equation and an approximate parabolic equation, the coal seam gas content coefficient α is fitted using the Langmuir adsorption curve equation. The fitting formula is: Wherein, W represents the methane content per unit volume of coal; a and b represent Langmuir adsorption constants. - Coal porosity; p - Coal seam gas pressure; B - Unit conversion coefficient; ρ - Apparent density of coal; α - Coal seam gas content coefficient; S5. After the flow meter's flow count stabilizes, the test of the cross-layer borehole is ended, and the corresponding coal seam gas content coefficient α is obtained. S6. After completing the previous borehole test, install the flow meter onto the extraction pipeline of the next borehole to be tested. Step 2: Accurate inversion of coal seam gas flow parameters: I. Using the theory of radial flow of gas in coal seams, a radially unsteady flow flow model of gas in coal seams is constructed, and the flow equation for the radially unsteady flow field in finite coal seams is obtained as follows: Where q is the gas emission per unit area; Y is the dimensionless flow rate; F0 is the dimensionless time rate; λ is the coal seam permeability coefficient; p0 is the initial gas pressure in the coal seam; p1 is the gas pressure in the borehole, which is 0.1 MPa when the atmosphere is vented; R1 is the borehole radius; α is the coal seam gas content coefficient; and t is the time. II. Based on the relationship curve between the flow rate number and the time number, the dimensionless equation for radially unsteady flow in a finite coal seam is obtained as follows: Where Y is the dimensionless flow rate; F0 is the dimensionless time rate; III. Construct the objective error function between the measured gas flow rate and the model gas flow rate. The objective error function is: Where ε is the error precision value. - Actual measured flow rate value - The model calculates the flow rate; IV. The coal seam gas flow parameters closest to the true value of the coal seam are obtained by inverting the coordinate rotation method; Step 3: Intelligent Evaluation of Coal Seam Gas Outburst Mitigation: ① Based on the coal seam gas flow parameters determined in step two; ② Based on the finite volume method, a fine numerical model for coal seam gas extraction is established using simulation software. The model is then divided into grids, and data on coal seam permeability coefficient, initial coal seam gas pressure, coal seam gas content coefficient, borehole radius, borehole thickness through coal seam, and borehole time are input. The forward modeling is then used to calculate the coal seam gas flow state. ③ Evaluate the outburst mitigation status of the coal seam based on the residual gas pressure and residual gas content calculated by simulation software. If the simulation results show that the residual gas pressure is <0.74 MPa and the residual gas content is <6.0 m³ / s, the outburst mitigation status is considered. 3 If the value is / t, the gas outburst suppression of the coal seam area is considered to meet the standard; otherwise, it does not meet the standard, and the outburst suppression evaluation of the extracted coal seam is completed. ④ Based on the actual conditions of the unextracted coal seam, pre-set different combinations of borehole radius, borehole spacing, and number of boreholes. Repeat step ② to establish a detailed numerical model of coal seam gas drainage under different combinations. Then, evaluate the outburst reduction status of different combinations through step ③ to select the combination that meets the gas outburst reduction standard for the unextracted coal seam. Among the selected combinations, select the one with the shortest drainage time as the optimal solution. The optimal solution will provide guidance for determining the actual drainage borehole spacing and drainage time for the subsequent extraction of the coal seam.

2. The intelligent evaluation method for coal seam gas extraction according to claim 1, characterized in that, The construction parameters for the cross-seam drilling include the construction angle, drilling radius, length of coal seam penetration, and drilling time.

3. The intelligent evaluation method for coal seam gas extraction according to claim 1, characterized in that, The sealing process employs a "two-plug-one-injection" pressurized sealing method.

4. The intelligent evaluation method for coal seam gas extraction according to claim 1, characterized in that, The coal seam gas flow parameters include the initial gas pressure of the coal seam and the coal seam permeability coefficient.

5. The intelligent evaluation method for coal seam gas extraction according to claim 4, characterized in that, The specific process of using the coordinate rotation method in step IV to derive the initial gas pressure and permeability coefficient of the coal seam that are closest to the true values ​​of the coal seam is as follows: i. Determine the initial values ​​of the initial gas pressure p0 and the coal seam permeability coefficient λ as the initial point X0 for iteration. (0) ; ii. At this point, keeping the coal seam permeability coefficient λ constant, a one-dimensional search is performed along the direction of the initial gas pressure p0. Before the search, the direction of descent of the target error function value is determined using a trial-and-error method, denoted as e1, thereby determining the optimal step size α1. At this point, the first iteration point X1 of the first round can be obtained. (1) =X0 (0) +α1 (1) e1; iii. Using X1 (1) Starting from this point, keeping the initial gas pressure p0 of the coal seam constant, a one-dimensional search is performed along the direction of the coal seam permeability coefficient. Before the search, the direction of descent of the target error function value is determined using the trial-and-error method, denoted as e2, thus determining the optimal step size α2. At this point, the second iteration point X2 of the first round can be obtained. (1) =X1 (1) +α2 (1) e2, at this point the initial gas pressure p0 and the permeability coefficient λ of the coal seam have completed the first iteration through two one-dimensional searches; iv. Continue iterating in the same way as above. As the iteration progresses, the target error function value decreases continuously. When the error accuracy value of the target error function is ≤1e-5, that is, when the accuracy requirement is met, the calculation ends. At this time, it means that the initial gas pressure and permeability coefficient of the coal seam have been inverted to be closest to the true value of the coal seam.

6. The intelligent evaluation method for coal seam gas extraction according to claim 1, characterized in that, The simulation software is COMSOL simulation software.

7. The intelligent evaluation method for coal seam gas extraction according to claim 1, characterized in that, The initial values ​​of the initial gas pressure and the initial permeability coefficient of the coal seam are determined based on the actual occurrence of gas in the coal seam.

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