A method for predicting methane concentration combination under buried pipeline leakage working condition

Abstract

The present application relates to buried pipeline leakage monitoring and prediction technical field, specifically relates to a kind of buried pipeline leakage working condition under methane concentration combination prediction method, obtain the methane concentration time history of monitoring point below leakage hole under benchmark condition and the methane concentration time history of monitoring point above leakage hole;Soil working condition increment item, aperture working condition increment item, buried depth working condition increment item and hydrogen sulfide content-pipeline pressure coupling increment item are constructed;The methane concentration prediction result of monitoring point below leakage hole and above leakage hole under target working condition is obtained by superimposing each increment item respectively with the methane concentration time history of corresponding monitoring point under the benchmark condition.The present application uses the modeling idea of benchmark response plus item correction, retains the main form feature of benchmark concentration time history;Second, by the way of singular value decomposition and least square fitting combination, multiple working condition concentration data is compressed into coefficient matrix and time base function vector, improve model calling efficiency.

Description

Technical Field

[0001] This invention relates to the field of buried pipeline leakage monitoring and prediction technology, specifically to a method for predicting methane concentration under buried pipeline leakage conditions. Background Technology

[0002] During the operation of buried oil and gas pipelines, once a leak occurs, the diffusion, migration, and accumulation of methane in the soil environment are influenced by factors such as pipeline pressure, soil properties, leak pore size, burial depth, and associated components. Rapid prediction of methane concentration time-series at the initial stage of a leak is beneficial for conducting leak risk assessments, deploying monitoring points, and developing early warning strategies.

[0003] Existing methods typically establish empirical relationships for single factors or a limited number of operating conditions, making it difficult to uniformly express concentration changes under the coupled effects of multiple factors while preserving the main characteristics of the baseline concentration curve. Especially when data for some operating conditions is incomplete, there remains a lack of effective solutions for converting existing experimental or simulation results into a combinatorial prediction model that can be assembled and generalized. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a combined prediction method for methane concentration under buried pipeline leakage conditions. By superimposing a baseline condition with incremental sub-items, the method integrates pipeline pressure, hydrogen sulfide content, soil density, pipeline burial depth, and leakage orifice diameter into the prediction model, enabling rapid acquisition of methane concentration curves under different conditions within a known sample range.

[0005] The technical solution of this invention is as follows: A method for predicting methane concentration under buried pipeline leakage conditions is as follows: Obtain the methane concentration time history at the monitoring point below the leak hole and the methane concentration time history at the monitoring point above the leak hole under the baseline operating conditions; Based on the target working conditions, we construct a soil working condition increment term that reflects the influence of soil density, an aperture working condition increment term that reflects the influence of leakage aperture, a burial depth working condition increment term that reflects the influence of pipeline burial depth and pipeline pressure coupling, and a hydrogen sulfide content-pipeline pressure coupling increment term that reflects the influence of hydrogen sulfide content and pipeline pressure coupling. The above incremental terms are superimposed with the methane concentration time history of the corresponding monitoring point under the benchmark operating condition to obtain the methane concentration prediction results of the monitoring point below and above the leak hole under the target operating condition.

[0006] The predicted methane concentration at the monitoring point below the leak hole under the target operating condition is as follows: ; The predicted methane concentration at the monitoring point above the leak hole under the target operating condition is as follows: ; In the formula: , The figures show the predicted methane concentrations at monitoring points below and above the leak hole under the target operating conditions. , The methane concentration time histories at monitoring points below and above the leak hole under baseline operating conditions are shown respectively. , These are the soil condition increments for monitoring points below and above the leakage hole, respectively. , These are the borehole diameter increments for monitoring points below and above the leak hole, respectively. , These are the hydrogen sulfide content-pipeline pressure coupling increments at the monitoring points below and above the leak hole, respectively. , These are the incremental terms for the burial depth of the monitoring points below and above the leakage hole, respectively. For time; This refers to the dimensionless hydrogen sulfide content. Dimensionless pressure; The dimensionless burial depth of the pipeline; These are dimensionless soil parameters; The leakage orifice diameter is dimensionless.

[0007] Specifically, the soil condition increment item is as follows: ; ; ; In the formula: This represents the soil feature vector; , These are the soil coefficient matrices for monitoring points below and above the leakage hole, respectively; , These are the soil time basis function vectors for the monitoring points below and above the leakage hole, respectively.

[0008] The aperture increment is specifically as follows: ; ; ; ; In the formula: The leakage orifice diameter feature vector; , These are the leakage orifice diameter coefficient matrices for monitoring points below and above the leakage orifice, respectively. , These are the time basis function vectors of the leakage hole diameter at the monitoring points below and above the leakage hole, respectively; The leakage orifice diameter.

[0009] The specific incremental items for burial depth conditions are as follows: ; ; in, ; In the formula: This is the feature vector for burial depth; , These are the burial depth coefficient matrices for the area below and above the leakage hole, respectively. , These are the burial depth time basis function vectors for the monitoring points below and above the leakage hole, respectively.

[0010] Specifically, the hydrogen sulfide content-pipeline pressure coupling increment term is as follows: ; ; in, ; ; In the formula: This is the hydrogen sulfide content-pressure coupled feature vector; The hydrogen sulfide-pressure coupling coefficient matrix for the monitoring point below the leak hole; The vector of time basis functions for hydrogen sulfide content-pressure coupling; The least squares slope between the concentration increments at the upper and lower monitoring points for soil conditions, burial depth conditions, and pore size conditions, respectively. is the time-varying transfer coefficient.

[0011] This also includes: converting the pipeline pressure, hydrogen sulfide content, soil density, pipeline burial depth, and leakage orifice diameter under the target operating conditions into dimensionless parameters, in the following order: dimensionless pressure. Dimensionless hydrogen sulfide content Dimensionless soil parameters Dimensionless pipeline burial depth and dimensionless leakage orifice diameter ; The specific process for obtaining dimensionless parameters is as follows: In the formula: For pipeline pressure; This refers to the hydrogen sulfide content; Soil density; For the depth of the pipeline; The leakage orifice diameter.

[0012] The specific determination process for the soil condition increment, pore size increment, burial depth increment, and hydrogen sulfide content-pipeline pressure coupling increment at the monitoring point below the leak hole is as follows: Construct concentration increment matrices for various operating conditions; Singular value decomposition is performed on the concentration increment matrix, and the first r principal components are taken as the time basis function vector, where the value of r satisfies that the cumulative singular value energy ratio is not less than a preset threshold η; the preset threshold η ranges from 0.95 to η to 0.999. Projecting each concentration increment matrix onto the corresponding time basis function vector yields the modal coefficient matrix; The relationship between the modal coefficient matrix and the eigenvectors is fitted using the least squares method to obtain the corresponding coefficient matrix; Then, the product of the eigenvector, coefficient matrix, and time basis function vector is used as the increment term.

[0013] The technical advantages of this invention are as follows: First, a modeling approach that uses a baseline response bonus term correction is adopted to preserve the main morphological characteristics of the baseline concentration time history; Secondly, by combining singular value decomposition with least squares fitting, the concentration data of various working conditions are compressed into coefficient matrices and time basis function vectors, thereby improving the efficiency of model calling. Third, for the missing hydrogen sulfide content-pipeline pressure coupling increment term at the upper monitoring point, a time-varying transfer coefficient is constructed using the upper and lower response relationships of other operating conditions to achieve approximate compensation of the missing term. Detailed Implementation

[0014] The present invention will be further described below with reference to embodiments thereof, but the scope of protection of the present invention is not limited to the following embodiments.

[0015] A method for predicting methane concentration under buried pipeline leakage conditions is presented below.

[0016] Step 1: Convert the pipeline pressure, hydrogen sulfide content, soil density, pipeline burial depth, and leakage orifice diameter under the target operating condition into dimensionless parameters, starting with dimensionless pressure. Dimensionless hydrogen sulfide content Dimensionless soil parameters Dimensionless pipeline burial depth and dimensionless leakage orifice diameter ; Then, feature vectors corresponding to various working conditions are constructed.

[0017] Step 2: Obtain the methane concentration time history at the monitoring point below the leak hole under the baseline operating conditions. and the methane concentration time history at the monitoring point above the leak hole under the baseline operating conditions .

[0018] Step 3: Construct the soil condition increment, pore size increment, burial depth increment, and hydrogen sulfide content-pipeline pressure coupling increment: Construct concentration increment matrices for various operating conditions; Singular value decomposition is performed on the concentration increment matrix, and the first r principal components are taken as the time basis function vector, where the value of r satisfies that the cumulative singular value energy ratio is not less than a preset threshold η; the preset threshold η ranges from 0.95 to η to 0.999. Projecting each concentration increment matrix onto the corresponding time basis function vector yields the modal coefficient matrix; The relationship between the modal coefficient matrix and the eigenvectors is fitted using the least squares method to obtain the corresponding coefficient matrix; The product of the eigenvector, coefficient matrix, and time basis function vector is used as the increment term to obtain the soil condition increment term, the pore size increment term, the burial depth increment term, and the hydrogen sulfide content-pipeline pressure coupling increment term at the monitoring point below the leak hole; among them, The soil condition increment includes: the soil condition increment at the monitoring point below the leak hole. and the soil condition increment item at the monitoring point above the leak hole ; The orifice diameter increment includes: the orifice diameter increment at the monitoring point below the leak orifice. and the borehole diameter increment item at the monitoring point above the leak hole ; The burial depth increment includes: the burial depth increment of the monitoring point below the leakage hole. and the incremental item of burial depth of the monitoring point above the leakage hole ; It also includes the hydrogen sulfide content-pipeline pressure coupling increment at the monitoring point below the leak hole. ; At each time point, the least squares slope of the concentration increment at the upper monitoring point relative to the concentration increment at the lower monitoring point is calculated for soil conditions, burial depth conditions, and pore size conditions. The arithmetic mean is then taken to construct the time-varying transmission coefficient. Furthermore, an incremental term coupling hydrogen sulfide content and pipeline pressure at the monitoring point above the leak hole is constructed. .

[0019] Step 4: Construct a methane concentration prediction model: The above incremental terms are superimposed with the methane concentration time history of the corresponding monitoring point under the baseline operating condition to obtain the predicted methane concentration at the monitoring point below and above the leak hole under the target operating condition; specifically: ; .

[0020] A specific application example is a method for predicting methane concentration under the condition of buried pipeline leakage, as shown below.

[0021] Step 1: Construct the feature vectors 1.1 Obtaining dimensionless parameters Target operating condition: pipeline pressure hydrogen sulfide content Soil density Pipeline burial depth Leakage orifice diameter ; The dimensionless conversion results are shown in Table 1: Table 1 Dimensionless transformation results 1.2 Constructing the feature vectors: Among them, soil feature vector ; Leakage aperture characteristic vector ; Burial depth feature vector ; Hydrogen sulfide content-pressure coupled eigenvector .

[0022] Step 2: Obtain the methane concentration time history at the monitoring point below the leak hole under the baseline operating conditions. and the methane concentration time history at the monitoring point above the leak hole under the baseline operating conditions .

[0023] Step 3: Construct the soil condition increment term, pore size increment term, burial depth increment term, and hydrogen sulfide content-pipeline pressure coupling increment term; as shown below.

[0024] I. Constructing the aperture operating condition increment term Using an 8mm leakage orifice diameter as the baseline operating condition, the concentration increment for each leakage orifice diameter relative to the baseline operating condition is calculated using the following formula. : (1) In the formula: Let be the methane concentration value corresponding to the operating conditions at time t. The methane concentration at time t represents the baseline operating condition. The concentration increment matrix of the leakage orifice diameter at monitoring points below the leakage orifice was obtained by selecting time points of 0.5, 1, 2, 5, 10, 20, and 50 s. and the concentration increment matrix of the leakage hole diameter at the monitoring point above the leakage hole. See Tables 2 and 3: Table 2. Leakage Hole Diameter Concentration Increment Matrix at Monitoring Points Below Leakage Holes Table 3. Matrix of Leakage Hole Diameter Concentration Increment at Monitoring Points Above Leakage Holes .

[0025] (1.1) Solve for the time basis function vector of the leakage hole diameter at the monitoring points below and above the leakage hole. 1.1.1 Singular Value Decomposition: Calculate using Table 2 as an example : ; 1.1.2 Eigenvalues ​​and Eigenvectors: The eigenvalues ​​obtained are: λ1≈0.612, λ2≈0.102, λ3≈0.056, λ4≈0.006, λ5≈0.001, λ6=λ7=0; 1.1.3 Singular value calculation: σ1≈ ≈0.782, σ2≈0.319, σ3≈0.237; The cumulative energy percentage of the first three principal components is as follows: Therefore, three principal components are selected; 1.1.4 Obtain the time basis function vector of the leakage hole diameter at the monitoring point below the leakage hole. : ; Similarly, the time basis function vector of the leakage hole diameter at the monitoring point above the leakage hole can be obtained from Table 3. : .

[0026] (1.2) Obtain the modal coefficient matrix Projecting the concentration increment matrix onto the corresponding time basis function vector yields the modal coefficient matrix; specifically: ; ; In the formula: The leakage orifice diameter modal coefficient matrix is ​​the monitoring point below the leakage orifice. This is the leakage orifice diameter modal coefficient matrix for the monitoring point above the leakage orifice.

[0027] (1.3) Obtain the leakage orifice coefficient matrix According to the definition of dimensionless aperture 5 sets of leakage orifice diameters corresponding to The values ​​are -3, -2, -1, 0, and 1, respectively, to construct the leakage orifice diameter characteristic vector under standard operating conditions. : ; Fit the modal coefficient matrix and the leakage orifice eigenvector under standard operating conditions using the following formula Relationship: In the formula: The leakage aperture modal coefficient matrix; by Alternative The leakage orifice diameter coefficient matrix of the monitoring point below the leakage orifice is obtained. : ; Similarly, the leakage orifice diameter coefficient matrix of the monitoring point above the leakage orifice is obtained. : .

[0028] (1.4) Predicting methane concentration ; At t=10s, the time basis function vector of the leakage orifice diameter at the monitoring point below the leakage orifice is: ; The borehole diameter increment term at the monitoring point below the leak hole is: .

[0029] II. Hydrogen sulfide content - pipeline pressure coupling increment Pipeline pressure hydrogen sulfide content Using the baseline operating condition as an example, five sets of hydrogen sulfide content-pipeline pressure coupled operating conditions (0.5, 1, 2, 5, 10, 20, 50 s) were selected to calculate the concentration increment matrix relative to the baseline operating condition. Table 5 shows the hydrogen sulfide content-pipeline pressure concentration increment matrix at the monitoring point below the leak hole. ; Table 4. Five sets of hydrogen sulfide content-pipeline pressure coupled operating conditions Table 5. Matrix of hydrogen sulfide content - pipeline pressure concentration increment at monitoring points below the leak. Table 5 provides the hydrogen sulfide content-pipeline pressure concentration increment matrix at the monitoring point below the leak hole. (5×7, corresponding to working conditions 1~5): .

[0030] (2.1) Solve for the hydrogen sulfide content-pipeline pressure time basis function vector at the monitoring point below the leak hole. 2.1.1 Singular Value Decomposition: Taking Table 5 as an example, calculate ,get 2.1.2 Eigenvalues ​​and Singular Values Solving the characteristic equation yields the non-zero eigenvalues: λ 22 =0.850, λ 32 =0.220, λ 42 =0.105, λ 52 ≈0.012, λ 62 ≈0.005, λ 72 ≈0.001; 2.1.3 Singular value calculation: ; The cumulative energy percentage of the first three principal components is as follows: Therefore, three principal components are selected; 2.1.4 Obtain the hydrogen sulfide content-pipeline pressure time basis function vector at the monitoring point below the leak hole. .

[0031] (2.2) Obtain the modal coefficient matrix ; In the formula: This is the hydrogen sulfide content-pipeline pressure modal coefficient matrix at the monitoring point below the leak hole.

[0032] (2.3) Obtain the hydrogen sulfide-pressure coupling coefficient matrix of the monitoring point below the leakage hole. According to the definition of dimensionless aperture and The q values ​​corresponding to the five hydrogen sulfide-pressure coupled operating conditions are [0.0182, -1], [1, -1], [1, -0.3846], [0.0545, 0], and [1, 0], respectively. A standard operating condition hydrogen sulfide content-pipeline pressure eigenvector is constructed. : ; Obtain the hydrogen sulfide content-pipeline pressure coefficient matrix at the monitoring point below the leak. : .

[0033] (2.4) Predicting methane concentration ; At t=10s, take , but .

[0034] III. Constructing incremental items for burial depth working conditions.

[0035] (3.1) Construct the depth-pressure concentration increment matrix of monitoring points below and above the leakage hole. Table 6. Matrix of Burial Depth-Pressure Concentration Increment for Monitoring Points Below Leakage Holes Table 7. Matrix of Burial Depth-Pressure Concentration Increment for Monitoring Points Above Leakage Holes .

[0036] (3.2) Obtain the burial depth time basis function vector of the monitoring point below the leakage hole. And obtain the burial depth time basis function vector of the monitoring point above the leakage hole. .

[0037] (3.3) Obtain the burial depth modal coefficient matrix of the monitoring point below the leakage hole. and the burial depth modal coefficient matrix of the monitoring point above the leakage hole ; .

[0038] (3.4) Obtain the burial depth coefficient matrix of the monitoring point below the leakage hole. Matrix of burial depth coefficients of monitoring points above the leakage hole .

[0039] IV. Constructing incremental items for soil working conditions.

[0040] (4.1) Construct the soil density concentration increment matrix at monitoring points below and above the leakage hole. Table 8. Soil density concentration increment matrix at monitoring points below the leak hole. Table 9. Soil density concentration increment matrix at monitoring points above the leak hole. .

[0041] (4.2) Obtain the soil time basis function vector at the monitoring point below the leakage hole. And obtain the soil time basis function vector of the monitoring point above the leakage hole. .

[0042] (4.3) Obtain the soil modal coefficient matrix at the monitoring point below the leakage hole. Soil modal coefficient matrix of monitoring points above the leakage hole ; .

[0043] (4.4) Obtain the soil coefficient matrix of the monitoring point below the leakage hole. Soil coefficient matrix of monitoring points above the leakage hole , .

[0044] V. Taking t=10s as an example, construct the time-varying transmission coefficient. .

[0045] (5.1) Soil conditions Non-benchmark soil density groups: 1650, 1800, 1875, 1950, 2025, 2100 kg / m³, at t=10s, with a soil density of 1725 kg / m³ 3 Based on the baseline, the soil density concentration increment x at the monitoring point below the leak hole 土壤 Soil density concentration increment y at monitoring point above the leak hole 土壤 See Table 10 below for details; Table 10 Non-benchmark soil conditions The calculation yields: .

[0046] (5.2) Burial depth conditions At t=10s, with a burial depth of 0.8m and a pressure of 6MPa as the baseline, the concentration increment x at the monitoring point below the leak hole is... 埋深 The concentration increment y at the burial depth of the monitoring point above the leak hole 埋深 See Table 11 below for details; Table 11 Non-reference burial depth working conditions The calculation yields: .

[0047] (53) Aperture working condition At t=10s, with a leakage orifice diameter of 8mm as the baseline, the concentration increment x at the monitoring point below the leakage orifice is... 孔径 The concentration increment y of the leakage hole diameter at the monitoring point above the leakage hole 孔径 See Table 12 for details; Table 12 Non-standard Leakage Orifices The calculation yields: ; and then: ; The same method was used to calculate for all discrete time points (0.5, 1, 2, 5, 10, 20, 50 s), and the following results were obtained: Table 13 Time-varying transmission coefficients As can be seen from the table, The value is relatively stable between 0.277 and 0.286, and the average value of about 0.28 can be taken as the simplified transmission coefficient.

[0048] 6. Calculate the concentration increment at the upper and lower monitoring points. Taking the target operating condition as an example, calculate the values ​​of each increment term at the monitoring points below and above the leakage hole at time t=10s. The dimensionless parameters have been determined as follows: .

[0049] (6.1) Hydrogen sulfide content-pipeline pressure coupling increment: ; .

[0050] (6.2) Soil working condition increment item: ; .

[0051] (6.3) Incremental items for burial depth conditions: ; .

[0052] (6.4) Aperture increment item: ; .

[0053] VII. Target operating condition prediction model (t=10s).

[0054] (7.1) Monitoring point below the leak hole Reference concentration , .

[0055] (7.2) Monitoring point above the leakage hole Reference concentration: , .

[0056] Conclusion: At t=10s, the predicted methane concentration at the monitoring point below the leak hole under the target operating condition is 0.7246, and the predicted methane concentration at the monitoring point above the leak hole under the target operating condition is 0.1762.

[0057] VIII. Model Validation The methane concentration at the monitoring point below the leak hole within 200 seconds after the leak occurred was calculated using both field test measurements and the combined prediction model of this invention. The results are shown in Table 1. Table 14 Comparison of experimental and predicted methane concentration values ​​at monitoring points below the leak hole under target operating conditions. .

[0058] As shown in Table 1 and the error indices, the predicted values ​​of the combined prediction model proposed in this invention are in good agreement with the actual measured values ​​at each time point. The average relative error is 2.46%, the root mean square error (RMSE) is 0.0184, and the coefficient of determination (R²) is [missing information]. 2 =0.9938. The maximum relative error occurred in the early stage of leakage, mainly due to the drastic change in the flow state and the sensor response delay at the moment of leakage; subsequently, the error quickly converged and stabilized within 3%, indicating that the model has good dynamic tracking ability.

[0059] Based on the above verification results, the methane concentration prediction method for buried pipeline leakage conditions proposed in this invention can accurately reflect the temporal variation of methane concentration at monitoring points below the leakage hole, with an average prediction accuracy better than 3%, and can explain more than 96% of the experimental data variation. This verifies the predictive reliability and engineering practical value of the model under multi-factor coupled conditions, and it can serve as an effective tool for buried pipeline leakage risk assessment and emergency decision-making.

Claims

1. A method for predicting methane concentration under buried pipeline leakage conditions, characterized in that, The method is as follows: Obtain the methane concentration time history at the monitoring point below the leak hole and the methane concentration time history at the monitoring point above the leak hole under the baseline operating conditions; Based on the target working conditions, we construct a soil working condition increment term that reflects the influence of soil density, an aperture working condition increment term that reflects the influence of leakage aperture, a burial depth working condition increment term that reflects the influence of pipeline burial depth and pipeline pressure coupling, and a hydrogen sulfide content-pipeline pressure coupling increment term that reflects the influence of hydrogen sulfide content and pipeline pressure coupling. The above incremental terms are superimposed with the methane concentration time history of the corresponding monitoring point under the benchmark operating condition to obtain the methane concentration prediction results of the monitoring point below and above the leak hole under the target operating condition.

2. The method for predicting methane concentration under buried pipeline leakage conditions according to claim 1, characterized in that, The predicted methane concentration at the monitoring point below the leak hole under the target operating condition is as follows: ； The predicted methane concentration at the monitoring point above the leak hole under the target operating condition is as follows: ； In the formula: , The figures show the predicted methane concentrations at monitoring points below and above the leak hole under the target operating conditions. , The methane concentration time histories at monitoring points below and above the leak hole under baseline operating conditions are shown respectively. , These are the soil condition increments for monitoring points below and above the leakage hole, respectively. , These are the borehole diameter increments for monitoring points below and above the leak hole, respectively. , These are the hydrogen sulfide content-pipeline pressure coupling increments at the monitoring points below and above the leak hole, respectively. , These are the incremental terms for the burial depth of the monitoring points below and above the leakage hole, respectively. For time; This refers to the dimensionless hydrogen sulfide content. Dimensionless pressure; The dimensionless burial depth of the pipeline; These are dimensionless soil parameters; The leakage orifice diameter is dimensionless.

3. The method for predicting methane concentration under buried pipeline leakage conditions according to claim 2, characterized in that, The specific soil condition increment item is as follows: ； ； ； In the formula: This represents the soil feature vector; , These are the soil coefficient matrices for monitoring points below and above the leakage hole, respectively; , These are the soil time basis function vectors for the monitoring points below and above the leakage hole, respectively.

4. The method for predicting methane concentration under buried pipeline leakage conditions according to claim 3, characterized in that, The aperture operating condition increment term is specifically as follows: ； ； ； ； In the formula: The leakage orifice diameter feature vector; , These are the leakage orifice diameter coefficient matrices for monitoring points below and above the leakage orifice, respectively. , These are the time basis function vectors of the leakage hole diameter at the monitoring points below and above the leakage hole, respectively; The leakage orifice diameter.

5. The method for predicting methane concentration under buried pipeline leakage conditions according to claim 4, characterized in that, The specific incremental term for the burial depth working condition is as follows: ； ； in, ; In the formula: This is the feature vector for burial depth; , These are the burial depth coefficient matrices for the area below and above the leakage hole, respectively. , These are the burial depth time basis function vectors for the monitoring points below and above the leakage hole, respectively.

6. The method for predicting methane concentration under buried pipeline leakage conditions according to claim 5, characterized in that, The specific incremental term of the hydrogen sulfide content-pipeline pressure coupling is as follows: ； ； in, ; ; In the formula: This is the hydrogen sulfide content-pressure coupled feature vector; The hydrogen sulfide-pressure coupling coefficient matrix for the monitoring point below the leak hole; The vector of time basis functions for hydrogen sulfide content-pressure coupling; The least squares slope between the concentration increments at the upper and lower monitoring points for soil conditions, burial depth conditions, and pore size conditions, respectively. is the time-varying transfer coefficient.

7. The method for predicting methane concentration under buried pipeline leakage conditions according to claim 1, characterized in that, This also includes converting the pipeline pressure, hydrogen sulfide content, soil density, pipeline burial depth, and leakage orifice diameter under the target operating conditions into dimensionless parameters, in the following order: dimensionless pressure. Dimensionless hydrogen sulfide content Dimensionless soil parameters Dimensionless pipeline burial depth and dimensionless leakage orifice diameter .

8. The method for predicting methane concentration under buried pipeline leakage conditions according to claim 7, characterized in that, The specific process for obtaining the dimensionless parameter is as follows: In the formula: For pipeline pressure; This refers to the hydrogen sulfide content; Soil density; For the depth of the pipeline; The leakage orifice diameter.

9. The method for predicting methane concentration under buried pipeline leakage conditions according to claim 2, characterized in that, The specific determination process for the soil condition increment, pore size increment, burial depth increment, and hydrogen sulfide content-pipeline pressure coupling increment at the monitoring point below the leak hole is as follows: Construct concentration increment matrices for various operating conditions; Singular value decomposition is performed on the concentration increment matrix, and the first r principal components are taken as the time basis function vector, where the value of r satisfies that the cumulative singular value energy ratio is not less than a preset threshold η; the preset threshold η ranges from 0.95 to η to 0.

999. Projecting each concentration increment matrix onto the corresponding time basis function vector yields the modal coefficient matrix; The relationship between the modal coefficient matrix and the eigenvectors is fitted using the least squares method to obtain the corresponding coefficient matrix; Then, the product of the eigenvector, coefficient matrix, and time basis function vector is used as the increment term.

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