Carboniferous Shale Gas Accumulation Characteristics and Exploration Directions in South China

Round 1

Reviewer 1 Report

The paper entitled " Carboniferous Shale Gas Accumulation characteristics and Exploration Directions in South China " provides through information about potential exploration value in the Dawuba Formation. The paper is well structured and well organized. I have the following comments:

1.      I recommend shortening the length of the abstract and highlighting what investigations have been done on the Dawuba Formation. The first several sentences on the background description look unnecessary with the current work but occupy too much length. The author described the exploration of Dawuba Formation as a significant breakthrough. If there can be more detailed data to support this meaningful exploration in the introduction part, it will be more convincing.

2.      There’s no inadequate information about the literature investigation on shale gas. I recommend adding more information about the types of kerogen with respect to maturity, and the characteristics of different types of kerogen. According to the results, samples from Dawuba Formation, kerogen types range from II to III, and they maybe gas-prone and oil-prone. Thus, more information is needed.   

3.      If possible, I recommend conducting Rock Eval analysis on the samples. Then plot the oxygen index and the hydrogen index of each sample in the figure, which provides a clear method to know the distribution of samples’ type.

4.      The authors state that “This new type of shale gas in South China shows promising potential and warrants further exploration and research” in page 17 lines 521-523, and “the exploration of shale gas in the region could have positive economic and environmental impacts, including reducing China's dependence on coal and decreasing greenhouse gas emissions” in page 1 lines 34-37. It would be great if the authors could address the environmental considerations associated with shale gas exploration like water contamination risks and the assessing of the overall environmental footprint of shale gas extraction.

5.      The authors mentioned that “has injected strong momentum into shale gas exploration” in page 1 lines 31-32. Please illustrate the strong momentum. Does this mean hydraulic fracturing?  Please provide a risk analysis regarding the uncertainties associated with shale gas exploration.

6.      Please address technical exploration information of QSD-1 well such as well performance, drilling challenges, and external factors like regulatory and market risks.

Please check the grammar, minor revision is needed. 

Author Response

We would like to thank the reviewer for the constructive comments.Here are the key modifications I’ve made to the article:

Response 1:

 I’ve rewritten the abstract to make it more concise while also adding crucial data on the characteristics of the Carboniferous shale in southern China. This ensures that the article is focused on a clear and consistent theme.

Response 2:

 I conducted a more thorough literature review, with a particular emphasis on analyzing kerogen types and maturity. I also added relevant research developments and analyses regarding Carboniferous organic matter to the article. (4.2 Organic geochemical characteristics )

Response 3:

 I added the oxygen index and the hyuddrogen index of each sample in the figure 5,  which displays “The main types and evolutionary pathways of the kerogen in the Dawuba Formation”. I also added corresponding descriptions of these indices in the text.

Response 4:

Based on feedback that “This new type of shale gas in South China shows promising potential and warrants further exploration and research,” we acknowledge that there is a lack of exploration and development data currently available for this particular stratigraphy. Therefore, we will continue our research efforts and build upon what we have learned so far. Thank you for offering this recommendation.

Response 5:

“as injected strong momentum into shale gas exploration” refers to the Carboniferous Shale talked in the pater. However, given the rapid changes in shale thickness and complex facies, exploration of this stratigraphy has significant uncertainty. The article has been supplemented with corresponding descriptions. (6 Conclusion)

Response 6:

 I’ve updated the technical exploration information of QSD-1 well in the section “5.2: Investigation direction of Upper Paleozoic marine shale gas in South China” .

Lastly, I conducted a thorough proofreading of the article, addressing grammar and sentence structure issues to ensure it meets the standards of language proficiency.

Reviewer 2 Report

This work provides a comprehensive study on the shale gas formation in Darwuba formation, in the carboniferous basin in south China. The paper provides an accurate geological and stratigraphic description, although some points, like the conditions of formation of the shale gas, and the mineralogy of the host rocks were not discussed. I missed some more discussion in figure 5, about the mineralogy revealed by SEM data. The discussion focuses just on pores, it is too little!

Also, some more details on the formations in the caption of figure 1: Dawuba Formation lithological characteristics. I would like the name of the formations, their age; names like slope, platform, are paleogeographical names, not formational.

Thes said, I found this paper well written, although somewhat limited in its scopes. A wider comparison on what is known for shale gas deposits world wide would be useful: I found just references from chinese authors, which makes one suspicious on the local charachter of this paper.

Author Response

We would like to thank the reviewer for the constructive comments. Here are the key modifications I’ve made to the article:

Response 1:
I have expanded the discussion in Figure 5 to include more information about the mineralogy revealed by SEM data.

Response 2:
I updated the file name for Figure 1 to include more specific information about formations, age, and sedimentary environment. This ensures that the figure is more easily identifiable and provides readers with a clearer understanding of the information presented.

Response 3:
I added more extensive coverage of the latest developments and research findings on Carboniferous shale gas exploration and research, both domestically and internationally. This was supplemented throughout the article and relevant sources were included in the references section.

Round 2

Reviewer 1 Report

I think the authors have resolved all issues and can be published in the current version. 

Please check the grammer and spelling again.