Backtracking to Parent Maceral from Produced Bitumen with Raman Spectroscopy

Round 1

Reviewer 1 Report

The paper deals with macerals and types of kerogen as I supposed coal deposit or shales. The authors use both reflectance and Raman spectroscopy to determine the type of kerogen. Although, the methods employed by the authors are correct, their observations and interpretations are justified, my overall impression is negative. The paper in the present form is not suitable for publication. However, the revision of the text can make it more appropriate for publication. I strongly encourage authors to revise this paper because there is much potential in the applied methodology and the results.

 

General remarks:

- There is no description of the geological background for the samples taken to analysis. In the text, there is only mentioned that samples cover a wide range of maturity but there is no detailed information about the burial of these sediments, temperature of maturation etc.

- There is no attempt to estimate the maturation temperature of the study particles by the method of Beyssac et al. 2002, Kouketsu et al. 2014 or Aoya et al .2010. It can be very useful in the interpretation, especially in the higher maturate OM.

 

Aoya M., Kouketsu Y., Endo S., Shimizu H., Mizukami T., Nakamura D., Wallis S. 2010 - Extending the applicability of the Raman carbonaceous-material geothermometer using data from contact metamorphic rocks. J. Metamorphic Geol., 28, 895–914, doi:10.1111/j.1525-1314.2010.00896.x

Kouketsu Y., Mizukami T., Mori H., Endo S., Aoya M., Hara H., Nakamura D., Wallis S., 2014 - A new approach to develop the Raman carbonaceous material geothermometer for low-grade metamorphism using peak width. Island Arc 23, 33–50. DOI:10.1111/iar.12057

 

- In the text, the table with data of Raman spectra peak decomposition e.g. peak position, heigh (maximum), FWHM should be inserted.

- The references are not formatted in the Minerals manner. Why the second author and the next authors start with a name while the first author starts with a surname?

- There is a lot of mistakes in citations in the text, e.g. there are citations that are not included in the reference list and vice versa. This should be corrected.

Detailed remarks are inserted in the text (reviewer copy).

Comments for author File: Comments.pdf

Author Response

Dear Respected Reviewer,

Thank you for taking the time to review our manuscript and providing us with constructive comments which will ensure the quality of this article to increase. In the attachment, you can respectfully find our response to the comments and amendments that are done accordingly.

Best Regards,

Mehdi

Author Response File: Author Response.pdf

Reviewer 2 Report

Backtracking to Parent Maceral from Produced Bitumen with Raman Spectroscopy

by Seyedalireza Khatibi et al.

 

The manuscript I reviewed is globally a good work. The threated topics are of course of interest and experimental methods used are adequate and suitable for the purpose. In general I think it is worthwhile to publish this work in Minerals. Nevertheless, I think there are some issues to adjust before publishing the manuscript.

First of all, I suggest a wide and deep revision of the work regarding the language and phrasal construction. Sometimes it is hard reading the text because of long periods, unconventional phrasal construction, typos, and some improper terms. I think some parts have to be re-written, while some other are almost fine. In the specific comments below I tried to underlie some of them and purpose some changes. The authors are free to accept or decline them.

Secondly, I think the manuscript is well-organized about the sequence of the threated topics, but sometimes some informations are lost (especially in the experimental section) and some parts could be deepened (e.g. introduction, results and discussion). I don’t know if the editing of Minerals is fixed, but in general I prefer to separate results from discussion in order to make clearer the dissertation. In this specific case, there are a lot of citations from other works, and previous works from the same authors: sometimes I found some confusion in understanding where all the data come from.

Finally, regarding data analysis and discussion, I found a good agreement between results and the interpretation the authors gave. Because my expertise is on Raman Characterization, I’ll focus on such part:

The authors state they perform a band deconvolution processing of Raman Spectra, but in the end they presented only the G and D5 band position. From literature, as the authors stated in the manuscript, it is well known that other parameters are suitable to investigate carbonaceous materials’ properties (e.g. D/G area or height ratioes, band width, …). All these data are not reported in the paper. I think it is important to show these data and eventually discuss if any of them show significant variations. Some other suggestion are reported in the specific comments.

For all these reasons I suggest a major revision of the text.

Specific comments:

16: I’d add a short sentence, stating the importance and power of Raman spectroscopy in studying carbonaceous materials and organic matter.

32-34: rephrase this sentence: it seems that something is lost and there is a repetition. Anyway the meaning is clear.

34-37: “the biogenic origin…”: in my opinion this sentence is not clear. It seems the authors want to explain the origin of kerogene, but in the following part of the sentence it is explained its composition (organic particulate matter and bitumen) and characterization methods. I think the topics (origin and composition) are useful in this dissertation, so I suggest the authors to better explain both in the introduction with different sentences. Accordingly, the characterization of such materials should be debated in a separate sentence because it is preparatory for the paper.

40: “programmed pyrolysis” in the introduction is referred as “programed”. I don’t know which is the right form, but I suggest the authors to uniform it in the text.

42: “with respect to”, probably “about” is more correct.

43-46: In my opinion the sentence should be rephrased: for example, “Kerogen characterization is not only useful…, but it also helps in developing models about…”

50-55: the paragraph is fine, but I’d divide it in three different periods. Even a numbered list referred to the previous sentence would be fine. In general I suggest the authors to use shorter sentences because it helps the reader in understanding the text.

55: “Table 1”: the authors should add it inside parenthesis or add a sentence.

62: “while”, maybe “despite” is more effective for this meaning.

69-70: the H/C O/C ratios: if are relevant to distinguish different types of kerogen should better debated and maybe added to Table 1. In any case, I’d re-write and move this sentence above, to the previous paragraph, related to the previous topic.

70-71: “Liptinite is included…”. this is a repetition, I’d cut it.

92: “is incapable of”. I don’t like it. Maybe “is not sensitive in” sounds better.

97-99: “Furthermore…”: Is suggest the authors to check some sentences in their structure because, despite the reader could understand their meaning, sometimes the text is hard to read. In this case, I’d rephrase as follows: “Furthermore petrographic approach cannot state whether solid bitumen, as an individual particle, is oil-prone or gas prone and, more in detail, what is the original maceral that produced the solid bitumen”.

116-119: “Raman spectrometers”. I’d move this sentence to line 112, after “chemical structures”. I’d also remove “easy to use” and I’d consider to use an abbreviation for Raman Spectroscopy (e.g., RS) because it is very frequent in the text.

120: I don’t like the word “demonstrate” in describing a purpose. Probably “investigate” or “study” is more suitable.

125: Samples preparation. From the text and Picture 1, I assume the samples grains casted in the epoxy resin were grinded for reflectivity measurements. The authors should explain this point. Then, are the same samples used for Raman analysis? These informations should be clearly stated in the text.

133: where

166-169: the authors have to provide more information about the experimental set up and acquiring conditions. Instrumentation brand and model, filtering system, spectrometer (grating and spectral resoltuion) and detector. Moreover the authors should report the acquisition conditions: laser power at the source and on the samples (2 mW is the laser source power or on the samples? Are the samples stable under this power?), acquisition time and accumulation cycles.

173: “mixed Gaussian–Lorentzian peak morphology“, is it Voigt or pseudo-Voigt profile? Is this approach taken from literature or is it a novelty of this approach? The authors should state these points and provide appropriate references. As stated above, I think the should report all the results of data fitting. I also suggest the authors to report the program and algorithms they used for band deconvolution, the Goodness of Fit (R %), and accurately describe the processing: sometimes band deconvolution processing could produce artifacts and I’d appreciate anyone could check the results.

178: Figure 2: in the figure appear two bands (in blue and pink). The authors should explain their meaning.

199: Figure 3: The results are very interesting, but I don’t understand the origin of all the plotted data. Are all these data from this work, are they from the cited work, or a mix of them?

232: Figure 4: Again, the results are interesting, but the current arrangement of this figure is complicated to “handle”. I suggest to merge all the plotted data in a single diagram, maybe stacking the lines. I also suggest to summarize the slopes and zero ordinate values of the regression lines in a table to better compare them.

246: Table 3. Previously the authors reported about H/C and O/C ratioes. They could be added to this table.

261: Because the authors refer about peak intensities and differences between different kerogen types, I suggest to add a figure comparing the Raman spectra. Sometimes, independently from deconvolution results, differences are barely clear from raw data…

307: reference is lost.

317: “programmed analysis” is probably “ programmed pyrolysis”

323: “G-band vs D5”. I think it should be clarified it is referred to peak position.

Author Response

Dear Editor and Respected Reviewers,

Thank you for taking the time to review our manuscript and providing us with constructive comments which will ensure the quality of this article to increase. In the attachment, you can respectfully find our response to the comments and amendments that are done accordingly.

Thank you and Best Regards,

Mehdi

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I agree with the changes in the text but I noticed some small mistakes in table 3 (capital letters should be started from the name).

As I pointed out in the first review, the references were still not formatted I and adjusted to the Minerals style. In the “Instructions for Authors” is written “... References must be numbered in order of appearance in the text...” but all references in the text are cited by names of authors (without numbers)

Comments for author File: Comments.pdf

Author Response

Dear respected reviewer,

Please see the attached file.

Regards,

Mehdi

Author Response File: Author Response.pdf

Reviewer 2 Report

The revised version of the manuscript is clearly improved with respect of the previous one. I appreciated the work made by the authors to make the text and the syntax clearer. I also appreciate that they accepted most of my suggestion of change. I still found some minor errors I reported below in the specific comments. I also still think that dividing results from discussion would make the manuscript clearer and understandable, but I respect the authors choice and point of view, and I think that this version is fine. Stated this, some doubts arise from some answers the authors gave about Raman analysis. I think there are some points that are not completely clear in the data processing and deconvolution. I have no doubts about the goodness of data and effectiveness of the results, but there are some “technical” errors that should be removed from the manuscript before publication. The main one, widely explained below in the specific comments, is the construction of Figure 4 and 5. They are based on the comparison with other works results: I couldn't check all the cited literature, but I'm afraid the results could be biased by a technical mistake (see specific comments). Anyway, I think the results and the outcomes of this work are consistent even without a direct comparison with other works.

I hope these suggestions could help the authors in improving the manuscript before the publication.

 

Specific Comments:

 

L.35: “local parameters” explain in parenthesis

L.36-38: I think something is missing in this sentence.

L.50: “to develop models in regard to” I've already reported in the previous revision this part of sentence. In my opinion is not clear and has to be changed.

L.85: remove “and,“

L.126: “utilize RS signals”, i'd change in: employ Raman spectra

L.142: “12200 to 12280 ft”, I suggest the authors to employ SI units. The same at L.145, 147 and 152.

Figure 1: The picture is nice, but I'd cut the “source” in the bottom of the picture and add it in the caption

L.185: “Figure 3”. Add in parenthesis or add a sentence above: “First order Raman spectrum... is reported in Figure 3”.

L.186: “In terms of spectral precision, the grating (1200 grating/mm) was not moved from one spot to another; therefore, there was not any change in the spectral calibration.” That's OK, but the resolution of the spectra is not reported.

L.194: I'd rephrase this sentence: e.g. “Raman Spectra were acquired...”

L.212: Figure 3 caption: “blue and purple bands are from CaCO3 that is present in samples”. I think there's something missing. The authors state the two bands are from CaCo3 (I suppose they are the reticular vibration at low frequencies and v4, in-plane bending), but there's no trace of symmetrical carbonate stretching, v1, in the picure. This peak is typically the stronger (several times with respect to the others) for carbonates, and should be present at about 1080cm-1. So I think the attribution to calcium carbonate is not correct. Because of the low intensity of all these peaks, I suggest the authors to remove them fro the image, because they could bring confusion and no useful information. Moreover, the picture denote that a baseline subtraction has been made: the author have to explain in detail this procedure in the experimental section. As stated in the previous revision, I'd appreciate an image of raw spectra.

L214: Table 3. I'd appreciate that all the peak parameters would be reported, maybe as Supporting Info. I know it's a lot of data, but it helps in understanding how the deconvolution process worked. e.g. I suggest the authors to follow the model of table used by Liu et al., 2013, in which are reported the peak parameters.

L.224: Figure4: I asked in the previous review about this point: the authors confirm that the data come, in part, from some other works and now state it in the caption. Of course is fine to match their data with others from literature, but my question arose from a doubt: I had no opportunity to check all the four papers cited, but the latter two (Sauerer et al, 2017 and Khatibi et al., 2018c) employ a different laser source (green 532 instead of red 633). I think it is a huge mistake comparing these sets of data with those from this work: in fact it is well known from literature that peak position and intensity for carbonaceous materials is strongly dependent on the laser source (see e.g. Bokobza et al., 2013) because of resonance effects (in particular band D). Clearly this effect will sum with the band shift due to the maturity of sediment, introducing a bias. Moreover in both the works I cited above, a different deconvolution approach is used (less peaks are used), and I think it could affect peaks positions and their intensity. In conclusion: in my  opninion the results are not comparable at all. Anyway, even without a direct comparison, I think it will not change the outcomes and the effectiveness of the results, but it is clearly a technical error which cannot be reported in a scientific paper.

Finally, in any case, if the authors make a picture mixing data from different works, for clarity I suggest to add in parenthesis, beside each mark in the legend, where the data come from.

L.244: progress

L.270: Figure 5. Again, the authors state that part of plotted data come from other works. I think in each diagram they should add the source. Scientifically speaking, I really appreciate this section, but I have the same doubt I explained for Figure 4. Because G-D is plotted and this value is dependent on laser source, I'm afraid the results could be technically affected by an inner bias. I could only check only Guedes et al., 2010 and Liu et al., 2013. The first used red 633, wile the latter used green laser 532nm as source. Moreover in Liu et al., 2013, it seems they used only two bands deconvolution model. I suggest the authors to check this point before any comparison, because the results could be strongly biased by the laser source employed. Eventually, compare only with Guedes et al, 2010, who used the same experimental conditions and processing model.

L.282-286: I think there is a mistake in Figure 6 (and consequently 7): it is correctly stated that the parameter which changes in different kerogens is sulfur content (TypeI<TypeIII<TypeII), but in the image TypeI<TypeII<TypeIII. Referring to Table3, it is clear that TypeII kerogen (WoodFord) has higher peak position for G e D5, so I suppose that Type II and TypeIII in the picture are swapped. Because of the large amout of data, as stated above, I suggest to better organize Table 3 which could help the reader in dealing with all these samples.

L.325-334: This part is fine. The authors made right observations supported by the data. Anyway, I've noticed that the difference between the two bitumen are more evident in peak G variation with respect of D5. I think the authors should comment this evidence. Is it in some way related to the content in aromatics and aliphatics, as stated for kerogen al L-306-310?

Author Response

Dear respected reviewer,

Please see the attached file.

Regards,

Mehdi

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

After the last aswers from the authors and the changes they made I think the manuscript is now fully corrected.

Some informations reported were not clear in the previous version, but now I find it is improved in the language and in the structure.

The last suggestion I have for the authors about the debate about the data acquired with different laser source, is to add in the text a sentence which state that the two sets of data are not directly comparable. Even if it is not the case, this is a common mistake I found in many papers I reviewed; so I think it is in any case better to remark it when data obtained with different sources are reported.