Sedimentary Provenance Analysis of Tight Sandstone Gas Reservoirs in the Middle Jurassic Shaximiao Formation, Western Sichuan Depression

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this manuscript, the sedimentary provenance characteristics of the Shaximiao Formation in the western Sichuan Basin was analyzed, multiple provenance analysis charts were established, and the provenance differences in different regions were determined. This paper has practical significance for the reservoir prediction of tight sandstone. The quality of the figures is high, however, the English writing of this paper should be improved. Minor revision is required on many points:

 

1: The unconformity between the Qianfoya Formation and the Baitianba Formation in the lithological profile of Figure 1b needs to extend to the left. Group member should be Formation.

2: The depth of the image of the rock core cross section in Figure 2 should be determined.

3: The abbreviation for Chemical Variation Index (CIA) should be italicized.

4: The annotation for Figure 5 has already appeared in Table 1, it is recommended to delete it.

5: It is recommended to keep the same number of decimal places as much as possible for data with similar properties in the paper.

6: The last paragraph of Ternary chart analysis in section 5.1.3 is a summary of the 5.1 Analysis of lithic fragment and should be included in the analysis in section 5.4.

7: There is an issue with the caption of Figure 8. It should be the distribution characteristics of heavy mineral index in the tight sandstone of Shaximiao Formation.

8: 5.3.1 The Analysis of Rare Earth Element Ratio does not describe the similarities and differences in data analysis across different regions. It seems to be a simple description of the data scope. Therefore, author still needs to conduct in-depth mining of the data.

9: It is suggested to split Figure 9 into two figures, so that readers can more intuitively perceive the subtle differences in the standardized curves of geochemical elements.

10: Figure 4 lacks a legend.

11: The vertical and triangular coordinates in Figure 10 are both missing units.

12: Line 476 486 rock debris - lithic fragment. Please check the full text about the use of rock debris.

13: What MDMTZ represents in Figure 11 is not mentioned in the article.

14: Line479-Stable heavy minerals can not only effectively suppress compaction and preserve primary pores.... This sentence is hard to believe. The content of heavy minerals is extremely low and they do not play a significant role in the rock formation process. The influence of the provenance on the reservoir quality still requires further analysis.

15: The conclusion does not reflect the provenance analysis conclusion obtained from the analysis of rock debris characteristics using trigonometric and radar charts. Suggest adding. The conclusion can be summarized into three points, which is sufficient.

 

 

 

 

 

 

Comments on the Quality of English Language

The English writing is relatively fluent, but there are some wrongs in the writing of terminology. For example, "rock debris" ，should be corrected throughout the text.

Author Response

Journal: Minerals

Submission ID: minerals-3960850

Paper Title: Sedimentary provenance analysis of tight sandstone gas reservoirs in the middle Jurassic Shaximiao formation, western Sichuan depression  

Authors: Xiao Luo, Dongxia Chen *, Shaoke Feng *, Qiaochu Wang

Dear Reviewer,

The authors are grateful for your letter and comments on our manuscript. The comments are very helpful for us to improve the quality of the manuscript. We have carefully revised the manuscript according to the editor and reviewers’ comments. All changes corresponding to the comments are marked in red color in the revised draft.

Corresponding authors: Dongxia Chen *, Shaoke Feng*

E-mail: lindachen@ cup.edu.cn; fsk962359370@163.com

Reviewer 1 comments:

General comments:

In this manuscript, the sedimentary provenance characteristics of the Shaximiao Formation in the western Sichuan Basin was analyzed, multiple provenance analysis charts were established, and the provenance differences in different regions were determined. This paper has practical significance for the reservoir prediction of tight sandstone. The quality of the figures is high, however, the English writing of this paper should be improved. Minor revision is required on many points: Response:

We thank the reviewer for your time and efforts in providing comments on our manuscript. Your comments are important for further improving the quality of this manuscript. We have revised the manuscript based on your suggestions. All the raised issues are addressed in this letter. The English writing of the article has been significantly improved under the guidance of Professor Chen and English professionals with geological expertise, based on the suggestions of the reviewers and the opinions of Reviewer 3 and Reviewer 4 on the English expression of the article.

Comments 1:

The unconformity between the Qianfoya Formation and the Baitianba Formation in the lithological profile of Figure 1b needs to extend to the left. Group member should be Formation.

Response 1:

Thanks for your helpful suggestion. According to your feedback, Corresponding modifications have been made to the unconformity between the Qianfoya Formation and the Baitianba Formation and header text in Figure 1b.

Please find the changes in lines 109.

Comments 2:

The depth of the image of the rock core cross section in Figure 2 should be determined.

Response 2:

Thanks for your great suggestion. We have confirmed the depth of the image of the rock core cross section in Figure 2.

Please find the changes in lines 121-124.

Comments 3:

The abbreviation for Chemical Variation Index (CIA) should be italicized.

Response 3:

This is a good recommendation. We have revised this content and checked and modified the entire article regarding this issue.

Comments 4:

The annotation for Figure 5 has already appeared in Table 1, it is recommended to delete it.

Response 4:

This is a good recommendation. We have removed the annotation below Figure 5.

Please find the changes in lines 248.

Comments 5:

It is recommended to keep the same number of decimal places as much as possible for data with similar properties in the paper.

Response 5:

This is a good recommendation. At the same time, based on the opinions of Reviewer 3 on the format of the article table, the decimal places of the data in the table have been standardized as much as possible, and the format of the table has also been improved.

Comments 6:

The last paragraph of Ternary chart analysis in section 5.1.3 is a summary of the 5.1 Analysis of lithic fragment and should be included in the analysis in section 5.4.

Response 6:

This is a good recommendation. We have placed the last paragraph of section 5.1.3 in the appropriate location of section 5.4.

Please find the changes in lines 392-401.

Comments 7:

There is an issue with the caption of Figure 8. It should be the distribution characteristics of heavy mineral index in the tight sandstone of Shaximiao Formation.

Response 7:

This is a good recommendation. Not only has the title of Figure 8 been modified, but the legend of Figure 8 has also been revised based on the comments of Reviewers 2 and 3.

Please find the changes in lines 305-306.

Comments 8:

5.3.1 The Analysis of Rare Earth Element Ratio does not describe the similarities and differences in data analysis across different regions. It seems to be a simple description of the data scope. Therefore, author still needs to conduct in-depth mining of the data.

Response 8:

Thanks for your great suggestion. The content of section 5.3.1 is already a detailed description of the data, while section 5.3.2 is a deeper exploration of the data in Table 5 of section 5.3.1.

Comments 9:

It is suggested to split Figure 9 into two figures, so that readers can more intuitively perceive the subtle differences in the standardized curves of geochemical elements.

Response 9:

Thanks for your great suggestion. We have divided Figure 9 into two figures (Figure 9 and Figure 10), which allows readers and Reviewer 3 to more intuitively perceive the subtle differences in the standardized curves of geochemical elements.

Please find the changes in lines 364 and 377.

Comments 10:

Figure 4 lacks a legend.

Response 10:

Thanks for your great suggestion. We have added the legend for Figure 4.

Please find the changes in lines 213.

Comments 11:

The vertical and triangular coordinates in Figure 10 are both missing units.

Response 11:

Thanks for your great suggestion. We have added the units of each coordinate in Figure 11 (original Figure 10).

Please find the changes in lines 388.

Comments 12:

Line 476 486 rock debris - lithic fragment. Please check the full text about the use of rock debris.

Response 12:

This is a good recommendation. The rock debris in the full text has been changed to lithic fragments.

Comments 13:

What MDMTZ represents in Figure 11 is not mentioned in the article.

Response 13:

Thanks for your great suggestion. The abbreviation in Figure 12 (original Figure 11) has been changed to the full name.

Please find the changes in lines 434.

Comments 14:

Line479-Stable heavy minerals can not only effectively suppress compaction and preserve primary pores.... This sentence is hard to believe. The content of heavy minerals is extremely low and they do not play a significant role in the rock formation process. The influence of the provenance on the reservoir quality still requires further analysis.

Response 14:

Thanks for your great suggestion. Corresponding modifications and deletions have been made to the inaccurate descriptions.

Please find the changes in lines 437-455.

Comments 15:

The conclusion does not reflect the provenance analysis conclusion obtained from the analysis of rock debris characteristics using trigonometric and radar charts. Suggest adding. The conclusion can be summarized into three points, which is sufficient.

Response 15:

Thanks for your great suggestion. According to the revised content of the article, corresponding modifications and optimizations have been made to the conclusions, and there are currently three conclusions.

Please find the changes in lines 447-473.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This paper provides a detailed study on sedimentary provenance of tight sandstone gas reservoirs in the middle Jurassic Shaximiao formation, western Sichuan depression. Several methods for provenance analysis have been clearly described, and the manuscript has novelty, making a certain contribution to the existing knowledge system and important application value for the exploration of tight gas reservoir in Sichuan basin.

The article suggests accepting after minor revisions.

1、The experimental method used in the article is not much different from the methods used by previous researchers. It is suggested to simplify this part of the content.

2、The formula in the Heavy Mineral Index method of the article needs to be referenced.

3、Suggest modifying the citation format according to the requirements of the journal.

4、The * of CaO in Formula 6 needs to be explained.

5、Pay attention to the legends of the figures, for example Figure 4 lacks a legend, while Figure 8 has more legends.

6、The first paragraph of section 4.3 seems to appear in the introduction.

7、Figure 6, Figure 7 and Figure 10 need to be labeled under the title of each image, simplify this part.

8、There seems to be a Chinese font shadow in Figure 7, which may be a minor oversight by the author and needs to be modified.

9、The legend Ati in Figure 8 has not appeared in the article, where it should be capitalized. This legend needs to be modified. Please also review the entire text and make revisions to similar issues.

10、The manuscript contains a large number of noun abbreviations. It is recommended that the author supplement with Nomenclature and Abbreviation.

11、The overall structure of the article is relatively reasonable, with relatively less content in section 4.2. It is recommended to merge the content of sections 4.2 and 4.3 under the title of Mineral and Elemental Experimental Analysis Results.

Author Response

Journal: Minerals

Submission ID: minerals-3960850

Paper Title: Sedimentary provenance analysis of tight sandstone gas reservoirs in the middle Jurassic Shaximiao formation, western Sichuan depression  

Authors: Xiao Luo, Dongxia Chen *, Shaoke Feng *, Qiaochu Wang

 

Dear Reviewer,

 

The authors are grateful for your letter and comments on our manuscript. The comments are very helpful for us to improve the quality of the manuscript. We have carefully revised the manuscript according to the editor and reviewers’ comments. All changes corresponding to the comments are marked in red color in the revised draft.

 

Corresponding authors: Dongxia Chen *, Shaoke Feng*

E-mail: lindachen@ cup.edu.cn; fsk962359370@163.com

 

Reviewer 2 comments:

 

General comments:

This paper provides a detailed study on sedimentary provenance of tight sandstone gas reservoirs in the middle Jurassic Shaximiao formation, western Sichuan depression. Several methods for provenance analysis have been clearly described, and the manuscript has novelty, making a certain contribution to the existing knowledge system and important application value for the exploration of tight gas reservoir in Sichuan basin.

The article suggests accepting after minor revisions.

 

Comments 1:

The experimental method used in the article is not much different from the methods used by previous researchers. It is suggested to simplify this part of the content.

Response 1:

This is a good recommendation. This part of the content has been deleted.

Please find the changes in section 3.1.

 

Comments 2:

The formula in the Heavy Mineral Index method of the article needs to be referenced.

Response 2:

This is a good recommendation. Corresponding reference citations have been added.

Please find the changes in lines 138-155.

 

Comments 3:

Suggest modifying the citation format according to the requirements of the journal.

Response 3:

This is a good recommendation. We downloaded the latest article on Minerals and made revisions for the citation format of the journal article.

 

Comments 4:

The * of CaO in Formula 6 needs to be explained.

Response 4:

Thanks for your great suggestion. We have added the meaning of *. CaO * refers to the CaO content in the non-chemical sedimentary part of rocks.

Please find the changes in lines 164-165.

 

Comments 5:

Pay attention to the legends of the figures, for example Figure 4 lacks a legend, while Figure 8 has more legends.

Response 5:

Thanks for your great suggestion. We have made modifications to the issues in Figures 4 and 8.

Please find the changes in lines 213 and 304.

 

Comments 6:

The first paragraph of section 4.3 seems to appear in the introduction.

Response 6:

This is a good recommendation. This paragraph has been included in the introduction.

Please find the changes in lines 56-74.

 

Comments 7:

Figure 6, Figure 7 and Figure 10 need to be labeled under the title of each image, simplify this part.

Response 7:

This is a good recommendation. There are already annotations for the regions in Figure 6, and additional annotations for the regions will be added in Figures 7 and 11 (original Figure 10).

Please find the changes in lines 283 and 390.

 

Comments 8:

There seems to be a Chinese font shadow in Figure 7, which may be a minor oversight by the author and needs to be modified.

Response 8:

Thanks for your great suggestion. We have made modifications to Figure 7.

Please find the changes in lines 281.

 

Comments 9:

The legend Ati in Figure 8 has not appeared in the article, where it should be capitalized. This legend needs to be modified. Please also review the entire text and make revisions to similar issues.

Response 9:

Thanks for your great suggestion. This is our mistake, we have made the revisions to the entire article regarding this issue.

 

Comments 10:

The manuscript contains a large number of noun abbreviations. It is recommended that the author supplement with Nomenclature and Abbreviation.

Response 10:

This is a good recommendation. We added Nomenclature and Abbreviation after the Conclusions of the article.

Please find the changes in lines 474.

 

Comments 11:

The overall structure of the article is relatively reasonable, with relatively less content in section 4.2. It is recommended to merge the content of sections 4.2 and 4.3 under the title of Mineral and Elemental Experimental Analysis Results.

Response 11:

This is a good recommendation. The content of sections 4.2 and 4.3 has been merged.

Please find the changes in lines 192.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors

I appreciate the authors' work.

The article requires significant revision, from the abstract to the results, discussion, and conclusions.

The article contains some inaccuracies in the language used.

The objective is not clearly defined. It is necessary to justify the relevance of the different methodologies used to obtain the desired results, as the objective is unclear.

The history of the formation and filling of the Sichuan Basin is not well described in the paper, particularly with regard to the main sediment supply paths over geological time.

The figures need to be improved and the tables formatted.

Additional comments and suggestions are provided in the attached PDF file.

Best regards

Comments for author File: Comments.pdf

Author Response

Journal: Minerals

Submission ID: minerals-3960850

Paper Title: Sedimentary provenance analysis of tight sandstone gas reservoirs in the middle Jurassic Shaximiao formation, western Sichuan depression  

Authors: Xiao Luo, Dongxia Chen *, Shaoke Feng *, Qiaochu Wang

 

Dear Reviewer,

 

The authors are grateful for your letter and comments on our manuscript. The comments are very helpful for us to improve the quality of the manuscript. We have carefully revised the manuscript according to the editor and reviewers’ comments. All changes corresponding to the comments are marked in red color in the revised draft.

 

Corresponding authors: Dongxia Chen *, Shaoke Feng*

E-mail: lindachen@ cup.edu.cn; fsk962359370@163.com

 

Reviewer 3 comments:

 

Comments 1:

The article requires significant revision, from the abstract to the results, discussion, and conclusions.

Response 1:

Thanks for your great suggestion. We have made detailed revisions to the article based on the reviewer's comments, with a focus on your suggestions in the attached PDF file.

For example:

1. Tight sandstone is a professional geological term, and the reservoir rocks of the Shaximiao Formation are mainly composed of tight sandstone.
2. The research area of the article is mainly focused on the western Sichuan depression. Therefore, the description of the entire text has been revised to the western Sichuan depression. The Western Sichuan Depression is also a commonly used geological term.
3. “However, in the Z region, well-developed fault systems in the western sector create a blocking effect on sediments derived from the front of the Longmenshan Thrust Belt (LMTB)”. It was not properly explained. We have clearly stated in the main text of the article that the development period of the fault is earlier than the sedimentation period, so we have modified the text description as follows:

“During the sedimentary period of the Shaximiao Formation, the Longquanshan Fault de-veloped in the Lower Jurassic had a blocking effect on the provenance from the front edge of Longmen Mountain in the west”.

4. “The higher content of limonite in area X indicates a higher degree of oxidation in its sedimentary environment, shallower water bodies, and closer proximity to the source area”. why? And the climate variation?

Limonite is a common type of iron ore, and its presence and content can serve as important indicators for determining the redox conditions of geological environments in geology. In an oxidizing environment, iron is easily oxidized to trivalent iron, forming limonite.

5. A revision is necessary because the authors do not make a clear distinction between results and discussion.

The results of the article only briefly describe the statistical results of some experimental data, but the discussion of the article is a deeper analysis of these data. Therefore, the structure of the article is reasonable.

 

Comments 2:

The article contains some inaccuracies in the language used.

Response 2:

Thanks for your great suggestion. The English writing of the article has been significantly improved under the guidance of Professor Chen and English professionals with geological expertise, based on the suggestions of the reviewers and the opinions of Reviewer 1 and Reviewer 4 on the English expression of the article.

 

Comments 3:

The objective is not clearly defined. It is necessary to justify the relevance of the different methodologies used to obtain the desired results, as the objective is unclear.

Response 3:

Thanks for your great suggestion. The objective of the article is to investigate the provenance characteristics of the tight sandstone reservoir in the Shaximiao Formation of the Western Sichuan Depression. There are four research areas, all located in the western Sichuan depression. Figure 1 also clearly indicates the scope of the study, the wells used in the study, and the study area.

 

Comments 4:

The history of the formation and filling of the Sichuan Basin is not well described in the paper, particularly with regard to the main sediment supply paths over geological time.

Response 4:

Thanks for your great suggestion. The suggestion made by the reviewer requires more research work to be carried out in order to achieve it, and more references to previous literature are also needed. At present, the information we have collected is insufficient to support this research. We will strengthen this aspect in our future research work.

 

Comments 5:

The figures need to be improved and the tables formatted.

Response 5:

This is a good recommendation. We have made the revisions to the figures and tables formatted based on the opinions of all reviewers.

 

Comments 6:

Additional comments and suggestions are provided in the attached PDF file.

Response 6:

Thanks for your great suggestion. We have made detailed revisions to the article based on the reviewer's comments, with a focus on your suggestions in the attached PDF file.

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Authors,

I have no crucial suggestion or request regarding your research. I found it is interesting and scientifically sound, although not completely "new". Data are well collected and proposed, results reliable, and interpretation coherent with results.

I found no reasons against publication.

Just a few points, I hope you may consider (please also see my comment about cited articles):

1) It's hard to follow the abstract when you refer to X, J, Z and Q Zones, they need to be introduced somehow. The same when you firstly introduce Cambrian at line 325.

2) Please adopt the correct style for in-text citations and references list (numerical rather than alphabetical order).

3) There's no need to constantly refer in full to the study area name, the Basin, the Formation, etc.: some sentences could be simplified.

4) Please pay attention to the correct use of geological terms: e.g., please do not mix chronological and lithostratigraphic terms (e.g., see lines 431-432).

Regards

The Reviewer

Author Response

Journal: Minerals

Submission ID: minerals-3960850

Paper Title: Sedimentary provenance analysis of tight sandstone gas reservoirs in the middle Jurassic Shaximiao formation, western Sichuan depression  

Authors: Xiao Luo, Dongxia Chen *, Shaoke Feng *, Qiaochu Wang

 

Dear Reviewer,

 

The authors are grateful for your letter and comments on our manuscript. The comments are very helpful for us to improve the quality of the manuscript. We have carefully revised the manuscript according to the editor and reviewers’ comments. All changes corresponding to the comments are marked in red color in the revised draft.

 

Corresponding authors: Dongxia Chen *, Shaoke Feng*

E-mail: lindachen@ cup.edu.cn; fsk962359370@163.com

 

Reviewer 4 comments:

 

I have no crucial suggestion or request regarding your research. I found it is interesting and scientifically sound, although not completely "new". Data are well collected and proposed, results reliable, and interpretation coherent with results.

I found no reasons against publication.

 

Comments 1:

It's hard to follow the abstract when you refer to X, J, Z and Q Zones, they need to be introduced somehow. The same when you firstly introduce Cambrian at line 325.

Response 1:

Thanks for your great suggestion. We have made modifications to this issue and gradually introduced some difficult to understand words.

 

Comments 2:

Please adopt the correct style for in-text citations and references list (numerical rather than alphabetical order).

Response 2:

This is a good recommendation. We downloaded the latest article on Minerals and made revisions for the citation format of the journal article.

 

Comments 3:

There's no need to constantly refer in full to the study area name, the Basin, the Formation, etc.: some sentences could be simplified.

Response 3:

Thanks for your great suggestion. We have made detailed revisions to the article based on the reviewer's comments, with a focus on your suggestions in the attached PDF file. On the basis of considering the level of understanding of the article by other reviewers, your question has also been improved to some extent.

 

Comments 4:

Please pay attention to the correct use of geological terms: e.g., please do not mix chronological and lithostratigraphic terms (e.g., see lines 431-432).

Response 4:

Thanks for your great suggestion. We have already addressed this issue.

Please find the changes in lines 392-401.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors

Thank you for your work.

I believe you were given an opportunity to improve your article.

The results presented could have been explained more clearly and consistently.

In line 372, the curve in the graph in Figure 10 is described as follows

“The curves as a whole present the characteristics of "four peaks, three valleys, and one flat", this description is very unclear without justifying the reasons for this pattern. I believe that the authors could improve the description they present.

The figures and tables have been kept in their original form. Even in Figure 1, was not even included a map showing the location of the study area within Chinese territory, forcing the reader to search for its location in previous works.

Of course, I respect your decisions, but I think it is clear that porosity was not properly described or discussed throughout the article. This is an article about sedimentary provenance.

I am attaching a new PDF with some notes that authors may find useful.

Best regards

Comments for author File: Comments.pdf

Author Response

Comments 1:

In line 372, the curve in the graph in Figure 10 is described as follows

“The curves as a whole present the characteristics of "four peaks, three valleys, and one flat", this description is very unclear without justifying the reasons for this pattern. I believe that the authors could improve the description they present.

Response 1:

Thanks for your great suggestion. Corresponding explanations have been added after this paragraph, as follows:

“The "four peaks" refer to the enrichment distribution characteristics of large ion lithophile elements Rb and Th, light rare earth elements La, Ce, and Nd, and high field strength ele-ment Zr. The "three valleys" refer to the distribution characteristics of depletion of large ion lithophile elements Ba and Sr and weak enrichment of light rare earth element Sm. The "three valleys" is indicative of large ion lithophile elements Ba and Sr depleted, while light rare earth element Sm fractionation remains subdued. The "one flat" refers to lack of high field strength elements Nb and Ta.”.

 

Comments 2:

The figures and tables have been kept in their original form. Even in Figure 1, was not even included a map showing the location of the study area within Chinese territory, forcing the reader to search for its location in previous works.

Response 2:

Thanks for your great suggestion. We have made detailed revisions to the article based on your comments, with a focus on your suggestions in the attached PDF file. The location of the research area in China has been added to Figure 1, and the font size of some of the images has been modified.

 

Comments 3:

Of course, I respect your decisions, but I think it is clear that porosity was not properly described or discussed throughout the article. This is an article about sedimentary provenance.

Response 3:

Thanks for your great suggestion. We have made modifications and deletions to this statement in the article.

Author Response File: Author Response.docx