PONE-D-21-40287Effect of different lithological assemblages on oil shale reservoir properties in the Permian Longtan Formation, southeastern SichuanPLOS ONE

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Additional Editor Comments:

This is an interesting integrative paper combining several different methodologies to define the relationships between the depositional environment, and the related lithologies, and the development of gas storage space. I appreciate the valuable contribution of the data presented here. However, certain issues need to be worked on before that paper can be published. The main issue is the writing that needs to be carefully edited throughout. I would suggest consulting a native speaker for a proper revision of English.

More problematic is the rather poorly developed introduction; it needs more attention for readers unfamiliar with the geology of this region to properly understand. The Reviewer highlights several significant issues throughout that need attention.

I noted the incompleteness of the figure captions, as did the reviewer, and a lack of accuracy in the drafting of the text (e.g., uncited figures).

According with the reviewer, I suggest operating major revisions, following the reviewer suggestions, to make the paper suitable for the publication.

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Reviewers' comments:

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Reviewer #1: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

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Reviewer #1: Yes

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Reviewer #1: No

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5. Review Comments to the Author

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Reviewer #1: Dear Editor,

Thank you for the opportunity to review the manuscript “Effect of different lithological assemblages on oil shale reservoir properties in the Permian Longtan Formation, southeastern Sichuan” (Manuscript: PONE-D-21-40287) by Qian Cao and Co-authors. This research focuses on the shale reservoir characteristic from different lithological assemblages of the Permian Longtan Formation in southeastern Sichuan. The authors seek to improve our understanding of the oil shale reservoir properties in the Longtan Formation by providing X-ray diffractometry (XRD), organic geochemistry, organic maceral identification, Ar-ion polishing, scanning electron microscopy (SEM), and N2 adsorption testing of samples collected for the abovementioned Formation. Overall, the quality of this research is good, and it will likely be of interest to a board audience.

In my opinion, this article in its current conditions required major revisions before to be accepted for publication on the PLOS ONE. I have several suggestions to improve the readability, accessibility, and impact of this research, and many of the more specific points are in the main reviewed space.

• I realize that the authors have a misleading in the meaning of Formation, i.e., in the Abstract section, the authors state that “the lithological development divides the Longtan Formation into lower (swamp), middle (tidal flat/lagoon) and upper (delta) sub-members” whereas, on the manuscript (section 3.1), the authors state that “the differences in the lithological assemblages in showed that Longtan Formation could be further divided into the Lower, Middle and Upper Longtan Formations.” From a stratigraphy point of view, a formation can be divided into members and grouped together in groups. Please, modify to lower, middle, and upper members.

• The main issue is the writing style that is quite poor in places and needs careful and thorough review to improve the clarity, conciseness, grammar, sentence structure, and organization. I accept that the authors may not be native English speakers, but the text would benefit from additional editing. I suggest the authors significantly polish the English or get the help of a native speaker. Some sentences are too long and entire paragraphs are too confusing for the reader. It should be made both more concise and sharper.

• The introduction should provide a better geographical context for readers not familiar with the study area.

• I encourage the authors to consider citing the figures of the manuscript (i.e., figure 7 is not cited at all on the manuscript).

• Figure captions are inadequate. Figure captions should be comprehensive but concise; they should clearly describe the contents of the figure; they should draw attention to key features in the figure. Figure captions should provide enough information so that the reader can easily review the figure without referring to the text. So, I would ask the authors to rewrite the figure captions.

• In figure 1, the authors should add a general map to better show the southeaster Block of the Sichuan Basin in Southern China and cite it in the introduction (section 1). In figure 1b, I motivate the authors to add the samples label of the 15 collected samples to show the exact stratigraphic position of each sample in the well-log. Always in figure 1b, it is too difficult to see the lithologies in the well-log.

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Reviewer #1: Yes: Anas Abbassi

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Attachments

Attachment

Submitted filename: PONE-D-21-40287_Anas Abbassi_Reviewer_Attachment.pdf

Effect of different lithological assemblages on shale reservoir properties in the Permian Longtan Formation, southeastern Sichuan Basin: Case study of Well X1

PONE-D-21-40287R1

Dear Dr. Qian CAO,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Paola Cipollari

Academic Editor

PLOS ONE

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