Comprehensive weighted matter-element extension method for the safety evaluation of underground gas storage

This study focuses on a safety evaluation method for underground gas storage. Gas storage is usually constructed underground in complex environments, and the service life of such facilities is limited. To ensure the secure and long-term operation of gas storage facilities, safety evaluation has become the focus of management. The present paper provides an effective method for safety evaluation. An index system was established as the foundation of the analysis for this evaluation, and the matter-element extension method was applied to obtain a quantitative evaluation result. For the weight values of each index in the matter-element extension method, this paper presents a comprehensive weight computation method based on vague sets and entropy. By application of this method, the safety level of a gas storage facility in the Jintan salt mines (in Jiangsu, China) was calculated, and the evaluation result was 4.6433, which meant the safety level was V and the underground gas storage was slightly at risk. It indicated that the influence on the overall safety and tightness of this gas storage could be ignored in the operation process, but the frequency of regular monitoring should be increased. The defective indexes were also obtained, such as salt rock cohesion, the roof thickness, the volume contraction ratio, the interlayer content, the height of the casing shoe and the adjacent cavity pressure difference, which need to be monitored and modified. This paper evaluated the safety of the underground gas storage from a unique perspective. It is expected that the results of this research will contribute to the maintenance and operational decisions, and provide a reference for management in the energy industry.


Comments to the Author(s)
The paper proposes a an index system for safety evaluation of underground gas storage, with an innovative approach based on the matter-element extension method. A few comments on the current manuscript: -the evaluation result in the abstract is relevant but it should be better explained, even if briefly, in the abstract. What does that mean? Is it high? Is it sufficient? What value other operations should aim at? -the objective of the research is explained in the second paragraph of page 3, but it would be important to explain here how the results are going to help other researchers evaluate their experiments replicating the proposed method.
-The explanation of the subjective method of choosing weights in Chapter 4 is somewhat confusing. I recommend the authors re-write the explanation with further details. And perhaps keeping the explanation of the choice of objective weights separated from the subjective weights.
-does the initial statement of section 4.1 come from a reference in the literature? -I recommend the discussion is expanded to examine alternative scenarios of subjective and objective weights if possible; -check spelling, for instance, why "Vague" has capital "V" in the conclusion?

Review form: Reviewer 2
Is the manuscript scientifically sound in its present form? Yes

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? No

Recommendation?
Major revision is needed (please make suggestions in comments)

Comments to the Author(s)
Manuscript Number: RSOS-191302 Title: Comprehensive Weighted Matter-Element Extension Method for the Safety Evaluation of Underground Gas Storage Journal name: Royal Society Open Science In this paper, the authors develop a safety evaluation method based on an index system was established and the matter-element extension method. The authors also use a comprehensive weight computation method based on vague sets and entropy for the weight values of each index in the matter-element extension method. Using the proposed safety evolution method, the author computing the safety level of a gas storage facility in the Jintan salt mines as 4.6433. In general, the manuscript has got some potential. The topic discussed in this manuscript is in high interest. the article offers some interesting perspectives and results. However, the manuscript needs some further improved before to be accepted for publication. The reviewer has listed some specific comments that might be helpful of the authors to further enhance the quality of the manuscript. Please consider the particular comments listed below.
1.Summary * Please highlight your scientific contribution 2. Introduction * The Introduction section is too short, some related information is missing. The reviewer believes that following references will enhance the background of the introduction section, please consider citing following papers: . Evaluating sustainability of water-energy-food (WEF) nexus using an improved matter-element 3. Matter-element extension evaluation method 4. Design of the comprehensive weighting calculation method * Detailed description of the source of the data, processing should be considered. * The method description is too long. Is it better to highlight your improvement of the method and your innovation in methods? 5. Application example for underground gas storage 6. Discussion The discussion section is two paragraphs. The two paragraphs form a separate section. It is recommended that the sixth section be combined with the fifth section.
7. Conclusion * I would suggest to write more explicitly the main findings of this study.

21-Jan-2020
Dear Dr Bi, The editors assigned to your paper ("Comprehensive Weighted Matter-Element Extension Method for the Safety Evaluation of Underground Gas Storage") have now received comments from reviewers. We would like you to revise your paper in accordance with the referee and Associate Editor suggestions which can be found below (not including confidential reports to the Editor). Please note this decision does not guarantee eventual acceptance.
Please submit a copy of your revised paper before 13-Feb-2020. Please note that the revision deadline will expire at 00.00am on this date. If we do not hear from you within this time then it will be assumed that the paper has been withdrawn. In exceptional circumstances, extensions may be possible if agreed with the Editorial Office in advance. We do not allow multiple rounds of revision so we urge you to make every effort to fully address all of the comments at this stage. If deemed necessary by the Editors, your manuscript will be sent back to one or more of the original reviewers for assessment. If the original reviewers are not available, we may invite new reviewers.
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Once again, thank you for submitting your manuscript to Royal Society Open Science and I look forward to receiving your revision. If you have any questions at all, please do not hesitate to get in touch. The paper proposes a an index system for safety evaluation of underground gas storage, with an innovative approach based on the matter-element extension method. A few comments on the current manuscript: -the evaluation result in the abstract is relevant but it should be better explained, even if briefly, in the abstract. What does that mean? Is it high? Is it sufficient? What value other operations should aim at?
-the objective of the research is explained in the second paragraph of page 3, but it would be important to explain here how the results are going to help other researchers evaluate their experiments replicating the proposed method.
-The explanation of the subjective method of choosing weights in Chapter 4 is somewhat confusing. I recommend the authors re-write the explanation with further details. And perhaps keeping the explanation of the choice of objective weights separated from the subjective weights.
-does the initial statement of section 4.1 come from a reference in the literature? -I recommend the discussion is expanded to examine alternative scenarios of subjective and objective weights if possible; -check spelling, for instance, why "Vague" has capital "V" in the conclusion?

Recommendation?
Accept as is

Comments to the Author(s)
Only minor corrections and adjustments are required along the text, such as spacing between " Table" and "6" in the discussion, and adjusting monitoring with capital "M" in the conclusions. The authors should review the entire manuscript accordingly prior to publication.

Review form: Reviewer 2
Is the manuscript scientifically sound in its present form? Yes

Are the interpretations and conclusions justified by the results? Yes
Is the language acceptable? Yes

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? No

Recommendation?
Accept as is It is a pleasure to accept your manuscript entitled "Comprehensive Weighted Matter-Element Extension Method for the Safety Evaluation of Underground Gas Storage" in its current form for publication in Royal Society Open Science. The comments of the reviewer(s) who reviewed your manuscript are included at the foot of this letter.
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