Numerical Simulation of CBM Seepage Characteristics Based on Fracture Network Images
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe study focuses on the influence of natural fracture networks in coal seams on gas migration. A discrete fracture network model was constructed using the voxel probability decomposition algorithm, and numerical simulations of gas migration and coalbed methane extraction were conducted, utilizing the image function in COMSOL. The relationship between permeability and structural parameters of the fracture network was also analyzed in detail. Overall, the paper is well-structured, and the research methodology demonstrates a certain level of novelty. I recommend the paper be published after minor revisions. Below are my detailed comments and suggestions.
1. The abstract and conclusion are somewhat lengthy and lack conciseness. It is recommended to break down long sentences and present the research content more directly.
2. In Section 2.3, when analyzing the speed and pressure of coalbed methane migration, it is suggested to include more quantitative expressions.
3. In Section 3, during the analysis of parameters, are the permeability variation values in Fig 4–9 analytical solutions from the voxel probability decomposition algorithm or results from numerical simulations?
4. In Section 3, are the fixed values or ranges of different parameters based on statistics from stereomicroscope scans, or are they typical values from actual engineering applications?
5. The specific values for parameters in Sections 3.1, 3.3, and 3.6 are not clearly stated.
6. In Section 4, regarding the analysis of simulation results for coalbed methane extraction, it is recommended to add quantitative expressions for the variations in speed and pressure.
7. The paper involves several parameters (e.g., porosity, fractal dimension, maximum fracture branch length, inclination angle, etc.), and it is suggested to add a sensitivity analysis for these parameters to explore their impact on the simulation results.
8. The statement in Lines 36-37 that needs to be by some previous papers, like: Establishment and evaluation of strength criterion for clayey silt hydrate-bearing sediments; Numerical simulation of fracture reorientation during hydraulic fracturing in perforated horizontal well in shale reservoirs
9. Since actual coalbed methane migration occurs in three-dimensional space, could the voxel probability decomposition algorithm be extended to construct a 3D fracture network model for future research?
Author Response
Responses to reviewers and editors
Manuscript title: Numerical Simulation of CBM Seepage Characteristics Based on Fracture Network Images
Manuscript ID：processes-3236686
Dear Editors and Reviewers:
Thank you for your email and for the reviewer’s comments concerning our manuscript entitled “Numerical Simulation of CBM Seepage Characteristics Based on Fracture Network Images” (processes-3236686). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the editor’ s and the reviewer’s comments are as follows.
Response to Editor: Thank you for your conscientious and responsible work for our manuscript. Meanwhile, thank you for giving us the opportunity to respond to the reviewers' comments and further improve the quality of the manuscript. After careful consideration and discussion, we gave detailed replies and modifications in response to the suggestions and questions raised by the reviewers.
Response to Reviewer #1:
General evaluation:
The study focuses on the influence of natural fracture networks in coal seams on gas migration. A discrete fracture network model was constructed using the voxel probability decomposition algorithm, and numerical simulations of gas migration and coalbed methane extraction were conducted, utilizing the image function in COMSOL. The relationship between permeability and structural parameters of the fracture network was also analyzed in detail. Overall, the paper is well-structured, and the research methodology demonstrates a certain level of novelty. I recommend the paper be published after minor revisions. Below are my detailed comments and suggestions.
Response: Thank you for your careful review and suggestions. Your suggestions are worth our careful consideration and proper adoption in our current and future research works.
Comments 1: The abstract and conclusion are somewhat lengthy and lack conciseness. It is recommended to break down long sentences and present the research content more directly.
Response 1: Thank you for your valuable suggestions. Based on your feedback, we have revised the abstract and conclusion to enhance the conciseness and readability of the text. The revised sections have been marked in red in the manuscript. Please review the updated version.
Comments 2: In Section 2.3, when analyzing the speed and pressure of coalbed methane migration, it is suggested to include more quantitative expressions.
Response 2: Thank you for your suggestions. We have conducted a quantitative analysis of velocity and pressure in Section 2.3 based on your recommendations. The revised sections have been marked in red in the manuscript. Please review the updated version.
Comments 3: In Section 3, during the analysis of parameters, are the permeability variation values in Fig 4–9 analytical solutions from the voxel probability decomposition algorithm or results from numerical simulations?
Response 3: Thank you for your suggestions. The permeability variation values in Figures 4 to 9 were plotted based on the numerical simulation results. I have revised the manuscript to make the structure clearer. The revised sections have been marked in red in the manuscript. Please review the updated version.
Comments 4: In Section 3, are the fixed values or ranges of different parameters based on statistics from stereomicroscope scans, or are they typical values from actual engineering applications?
Response 4: Thank you for your suggestions. The fixed values or ranges of the parameters in Section 3 were determined based on typical values from actual engineering practices. The selection of these parameters was referenced from relevant literature and common data in engineering practice to ensure the simulation results are realistic and applicable. We have further clarified this point in the manuscript. Please review the revised version.
Comments 5: The specific values for parameters in Sections 3.1, 3.3, and 3.6 are not clearly stated.
Response 5: Thank you for your valuable suggestions. Based on your feedback, we have added specific parameter values in Sections 3.1, 3.3, and 3.6. The revised sections have been marked in red in the manuscript. Please review the updated version.
Comments 6: In Section 4, regarding the analysis of simulation results for coalbed methane extraction, it is recommended to add quantitative expressions for the variations in speed and pressure.
Response 6: Thank you for your suggestions. Based on your feedback, we have conducted a quantitative analysis of velocity and pressure in Section 4. The revised sections have been marked in red in the manuscript. Please review the updated version.
Comments 7: The paper involves several parameters (e.g., porosity, fractal dimension, maximum fracture branch length, inclination angle, etc.), and it is suggested to add a sensitivity analysis for these parameters to explore their impact on the simulation results.
Response 7: Thank you for your suggestions. We fully recognize the importance of parameters such as porosity, fractal dimension, maximum fracture branch length, and dip angle in influencing the simulation results. Due to space limitations and data processing constraints, a detailed sensitivity analysis of these parameters was not included in this study. However, we plan to focus on this aspect in future research, systematically exploring the impact of different parameters on the simulation results and further improving the predictive capability of the model. We appreciate your support for our research and will actively incorporate your suggestions in future studies.
Comments 8: The statement in Lines 36-37 that needs to be by some previous papers, like: Establishment and evaluation of strength criterion for clayey silt hydrate-bearing sediments; Numerical simulation of fracture reorientation during hydraulic fracturing in perforated horizontal well in shale reservoirs.
Response 8: Thank you for your suggestions. Based on your feedback, we have added references in the relevant sections. The revised parts have been marked in red in the manuscript. Please review the updated version.
Comments 9: Since actual coalbed methane migration occurs in three-dimensional space, could the voxel probability decomposition algorithm be extended to construct a 3D fracture network model for future research?
Response 9: Thank you for your valuable suggestions. We recognize the complexity of actual coalbed methane migration in three-dimensional space. In this study, due to time constraints and limited computational resources, we employed a simplified two-dimensional model for the simulation analysis. However, in future research, we plan to use a voxel-based probability decomposition algorithm to construct a three-dimensional fracture network model, providing a more comprehensive representation of coalbed methane migration in complex fracture networks. We appreciate your support for our research and will actively pursue this direction to enhance the applicability of the model.
We are very grateful to the reviewers for their numerous suggestions and questions. The above content contains our detailed responses to the comments from the reviewers. We tried our best to improve the manuscript and made appropriate changes, and these changes will not influence the main content of the paper. In addition, we appreciate for Editors/Reviewers’ warm work earnestly, and hope that the manuscript after the corrections can satisfy the requirements for publication. Once again, thank you very much for your careful review.
Yours sincerely,
Wenbin Li. on behalf of the authors.
Corresponding Author: Yongjian Zhu. E-mail: yjzhu@hnust.edu.cn.
School of Resources and Environment and Safety Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsDear Authors,
A manuscript entitled: Numerical simulation of CBM seepage characteristics based on fracture network images discussed the established model of CBM characteristics based on the discrete method. The method is described as a mathematical/computational framework designed to represent the complex spatial
arrangement and interaction of cracks. In such a system, the geometry of individual cracks, including their orientation, length, aperture, and connectivity, is explicitly modeled, allowing users to analyze crack network behavior under various loading conditions, or porosity and permeability.
The authors provided a good state-of-the-art discussion where they provided valid international references on most important papers. Moreover, the manuscript is well organized. It provides a good discussion and results support conclusions.
What I am missing is the information about the processing of the images in terms of noise removal. In my opinion, this information should be included by the authors. Also what the authors could provide is the general figure on data processing workflow which would inform readers about all required operation and processing options.
Yours sincerely
Reviewer
Author Response
Responses to reviewers and editors
Manuscript title: Numerical Simulation of CBM Seepage Characteristics Based on Fracture Network Images
Manuscript ID：processes-3236686
Dear Editors and Reviewers:
Thank you for your email and for the reviewer’s comments concerning our manuscript entitled “Numerical Simulation of CBM Seepage Characteristics Based on Fracture Network Images” (processes-3236686). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the editor’ s and the reviewer’s comments are as follows.
Response to Editor: Thank you for your conscientious and responsible work for our manuscript. Meanwhile, thank you for giving us the opportunity to respond to the reviewers' comments and further improve the quality of the manuscript. After careful consideration and discussion, we gave detailed replies and modifications in response to the suggestions and questions raised by the reviewers.
Response to Reviewer #2:
General evaluation:
A manuscript entitled: Numerical simulation of CBM seepage characteristics based on fracture network images discussed the established model of CBM characteristics based on the discrete method. The method is described as a mathematical/computational framework designed to represent the complex spatial arrangement and interaction of cracks. In such a system, the geometry of individual cracks, including their orientation, length, aperture, and connectivity, is explicitly modeled, allowing users to analyze crack network behavior under various loading conditions, or porosity and permeability. The authors provided a good state-of-the-art discussion where they provided valid international references on most important papers. Moreover, the manuscript is well organized. It provides a good discussion and results support conclusions.
Response: Thank you for your careful review and suggestions. Your suggestions are worth our careful consideration and proper adoption in our current and future research works.
Comments 1: What I am missing is the information about the processing of the images in terms of noise removal. In my opinion, this information should be included by the authors.
Response 1: Thank you for your valuable suggestions. Based on your feedback, we have added specific methods and steps for image noise removal in the relevant sections of the manuscript and provided detailed explanations of the techniques used. The revised parts have been marked in red in the manuscript. Please review the updated version.
Comments 2: Also what the authors could provide is the general figure on data processing workflow which would inform readers about all required operation and processing options.
Response 2: Thank you for your suggestions. We have provided a detailed description of the key steps and methods used in data processing within the manuscript to ensure that readers can understand our processing workflow and operational options. The revised sections have been marked in red in the manuscript. Please review the updated version.
We are very grateful to the reviewers for their numerous suggestions and questions. The above content contains our detailed responses to the comments from the reviewers. We tried our best to improve the manuscript and made appropriate changes, and these changes will not influence the main content of the paper. In addition, we appreciate for Editors/Reviewers’ warm work earnestly, and hope that the manuscript after the corrections can satisfy the requirements for publication. Once again, thank you very much for your careful review.
Yours sincerely,
Wenbin Li. on behalf of the authors.
Corresponding Author: Yongjian Zhu. E-mail: yjzhu@hnust.edu.cn.
School of Resources and Environment and Safety Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAccepted
