Review of NMR Studies for Oilwell Cements and Their Importance
Round 1
Reviewer 1 Report
This manuscript is appropriate as a Reviewit raises a topical issue presented by a review of the literature.
The first picture should be adjusted as it is not very informative
but draws a lot of attention to itself. The first tabele is very interesting with good structure.
Author Response
This manuscript is appropriate as a Review.
it raises a topical issue presented by a review of the literature.
The first picture should be adjusted as it is not very informative but draws a lot of attention to itself.
ANSWER: thank you for your suggestion we have update the figure.
The first table is very interesting with good structure.
ANSWER: thank you for taking time to review our paper.
Reviewer 2 Report
Review of paper: Review of NMR Studies for Oilwell Cements and their Importance.
This is a review paper on the application of NMR in studying oil well cement during hydration and post hydration. In terms of relevance, the scope is relevant to the oil and gas industry, hence, the journal. On the other hand, the paper is lean in its content comparing to a review article. The focus is only on the past works directly in cementing. However, NMR is a common method used for many other applications such as pore size distribution analysis in porous media that is directly transferable to the cement structure studies. Also, since the author brought up other methods such as CT scanners, they should at least try to explain why NMR is superior in this domain as per the claim. The paper mostly read as if it is about the process of cement hydration and porosity and not so much on the NMR method and its variants. In this case, the title is misleading.
Overall, I feel the paper can be considered for publication provided that the authors address my main comment above. The scope of the review is too narrow for a review article, and the authors need to broaden their literature survey. There are many instances of applications of NMR in the porous media community that can be directly applied to the problem of interest in this study.
Other than the above comment, some minor changes need to be addressed. Notation in the paper is not consistent and constantly changes. For example, T1 and T2 are sometimes written as subscripts and other times just T1 and T2. Some abbreviations are not defined. Figures are unusually large for a journal paper. There are quite a few grammatical and structural issues with the writing as well. For instance, line 1 of introduction: "...contain pores that a filled with a fluid, typically...", the article a is unnecessary and should be are. Please note I am not going to list all the problems as there were quite a few.
Author Response
Answer: Thank you for your comments. We fully understand the scarcity of NMR papers focused on well cements, but this is why we believe our paper is string: to highlight the importance of NMR.
We have added a paragraph explaining why NMR is superior to other methods. Also the reviewer is right, our intent is to focus on NMR cement studies only, since the existing literature on NMR on rocks is too large and will dilute our paper.
We also followed your recommendation and correct the found spelling and other errors.
Reviewer 3 Report
Thanks for the author's effort on summarizing current research extent of using NMR to understand cement properties in oil wells. Overall, the summary lacks in substance. This can be explained in small amount of published research available in the topic of NMR studies for oil well cement as authors explained. For that reason I suggest this manuscript for publication with minor revisions as it is not the fault of authors that there is not much research in NMR for oil wells. This paper should serve as call for more research in NMR for oil wells.
- Please include nomenclature. There are abbreviations in the paper that authors did not specify such as C-S-H?
- Check for spelling errors throughout the paper such as in 74.
- What exactly benefit of knowing:
- Porosity and T2 relaxation Time Comparison?
- Effect of cement mixing on NMR porosity measurements?
for oil fields? How does it help us to learn more about integrity of cement job? Please elaborate in the paper.
- Also if authors elaborate more on how actually NMR is used in field conditions to assess cement integrity would be valuable, too. How it can be improved ?
Author Response
Thank you for your comments to help improving our paper.
Answer: C-S-H was already defined in the abstract. Based on your suggestion a nomenclature section has been also included
Answer: Thank you for advice, we have fully checked the paper
Answer: cement porosity is a critical parameter for oil well cements since they are used to seal the well. The T2 in NMR studies allows to understand the porosity level
Answer: The NMR studies are to be performed in the laboratory which allows the scientist to develop better cement recipes that can be used in the field. For example, a cement that develops extreme low permeability in a short time will lead to better well integrity. Our studies shows that the mixing of the cement will result in different NMR response, hence the low porosity development can be affected by the mixing process.
Answer: as mentioned above our goal is not to use NMR in the field yet. The main reason is that very few NMR studies have been done on cements. However, if we fully understand the cement hydration process and its porosity changes we can create better cement recipes.
Round 2
Reviewer 2 Report
The authors made some changes to the manuscript, addressing some of the comments from the earlier version. I think the paper can proceed to the publication stage.
