Deep-Sea Sediment and Water Simulator for Investigation of Methane Seeping and Hydrate Formation

Round 1

Reviewer 1 Report

The topic of this paper is very important in the research field of the ubiquitous methane seeping . This paper presents a newly-built deep-sea sediment and water simulator, and conducts a group of experiments, and analyzes the methane seeping and hydrate formation. It is suitable for publication in this journal from the topic of this paper. I would suggest a moderate correction for this paper before it can be accepted for publication. The detailed comments listed below can be useful for the authors in improving their manuscript.

1. In the introduction, this part of "However, the rise of marine temperature, geological movement and the NGH exploitation all may lead to the hydrate dissociation and CH4 leakage" needs to be added with references.
2. The deep-sea sediment used in this paper is sand. Can cohesive soil be considered? As far as the reviewer understands, a large portion of deep-sea sediments are clayey soils, especially surface sediments. Some data can be beneficial to this paper. For examples: “Evaluation of undrained shear strength of surficial marine clays using ball penetration-based CFD modelling. Acta Geotechnica.”and “Centrifuge experiment on the penetration test for evaluating undrained strength of deep-sea surface soils. International Journal of Mining Science and Technology.”. In addition, the source, preparation and physical and mechanical parameters of sediment samples need to be described in detail.
3. There is an error in line 115 for the full angle symbol.
4. The various sensor types, test ranges and accuracies should be clearly displayed in a table.
5. Based on the presentation of the test results, it is suggested that the camera system (including light source) needs to be optimized and adjusted.
6. What is the maximum simulated water depth that can be achieved by the developed device?
7. The scales in Figures 12 and 13 are missing units.
8. Please check the vertical coordinates of Figure 15.
9. Section 3.2.4 shows only the phenomenon and lacks analysis.
10. Some equations should be added to the text to explain in detail how to obtain these physical quantities by experiment.
11. The font size of the reference is too large. The clarity of many figures in the manuscript needs to be increased. In addition, many fonts and sizes in figures are large or small, which need to be adjusted uniformly.
12. It is recommended that the conclusions of Chapter 4 are shown in points.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript introduces the gas seep and hydrate formation experimental system with the artificial deep-sea sediment and water environment. I believe that this system is unique (instead of a simple hydrate formation/dissociation experiment) and has a potential to serve for a better understanding of the actual CH4 release system across the seafloor. The system is briefly but well documented, with necessary sensors (T, R), monitoring devices, and sampling ports provided.

I agree with publication of this manuscript with some (minor) correction as suggested below and in the attached PDF file. I am afraid that some sentences are not correctly written. I tried to modify but please ask for the native check.

 

Major comments

What is the cause for the initial increase in resistance, CH4 concentration, and cumulative volume increase of gas? The interpretations will be discussed in the later work, but I wonder how much gas is ‘leaking’ through the inlet to the outlet (instead of solute to the water or forming hydrate) may be of interest in this article.

In 3.2.1 Resistance variation (and in Fig. 11), we recognize 3 major events in R13. The first (2.58h) is interpreted in the text (growth of CH4 hydrate around R13), but not the second (~10h) and third (~120h) events. The 120h event is correlated with the gas concentration change (Fig. 14 & 15). Is there any possible interpretation on these? I understand that this manuscript is focused on the ‘validation’ of the system, but some implication can help readers for a better understanding or even assessment of the apparatus.

Maybe, a cartoon explaining the possible phenomena (time-lapse) is helpful. However, a text-based scenario is also fine here.

 

I am not familiar with the laboratory experiments made so far.

 

Minor comments

See the attached PDF file for more suggestions (all editorial).

‘resistance’ à ‘electric resistance’ (not all, but on its first appearance at least).

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf