Four-Dimension Seismic Analysis in Carbonate: A Closed Loop Study
Round 1
Reviewer 1 Report
Dear Authors,
First of all many thanks for submitting an interesting paper. I overall enjoyed the read and like that you have chosen specifically 4D seismic in carbonate for a closed loop case for reservoir production properties estimations.
The first part of the paper summarizes the 4D seismic workflow is developed with a 1D well-based 4D feasibility to detect the likelihood of 4D signals before performing 4D seismic co-processing of the baseline and monitor surveys starting from the seismic field data of datasets.
Then finally, they have matching the 4D seismic signal with changes in reservoir production properties and assisted in investigating the mechanism underlying the observed 4D signal. It was found that the detectability of 4D signals is primarily related to changes in fluid saturation in the reservoir, which increase from 1994 to 2014.
I found especially the methodological part relatively unclear. Some of this confusion is quite likely caused by the often-unprecise use of the English language, but also stems from a certain lack of scaling in the results, and too small technical elaboration on data parameters and results, while the description of the proposed workflow is also missing. It would be better for the reader if you can provide workflow in a graphical form.
Some minor corrections:
Table 1. need to redraw the table with a similar text format.
Figure 1. the log scale and name on top are unreadable. You can provide a higher resolution figure.
In figure 4, what the highlighted yellow represents.
What is the purpose of table 2 here? Please relate it as it looks like a legend of color.
Figure 6 is too blurry. I would suggest making each part separate and or maybe top and bottom separate to make it visible.
It is better to choose a white background for figures 9 and 10 If possible.
In Conclusion, the author needs to highlight the contribution of the paper with a complete sentence.
Some references missing in the literatures dealing with heterogeneous carbonates are given as under. These studies could improve the scientific understanding of carbonates.
· Ali, A., Sheng-Chang, C., & Ali, S. H. (2022). Integration of Density-Based Spatial Clustering with Noise and Continuous Wavelet Transform for Feature Extraction from Seismic Data. Pure and Applied Geophysics, 1-13.
· Thank you.
Author Response
Please see the attachment for Author's response to the reviewer.
Author Response File: 
Author Response.docx
Reviewer 2 Report
It is an interesting topic about 4D seismic study in carbonate reservoir proposed by the authors. There are some comments that needs to be made before publication as follows:
1. At the very beginning of manuscript, the authors need to discuss about the reservoir properties specifically the fluid types, API, GOR, temperature, pressure, production data, PVT, the history of the field, the year of production, year of injection, the year seismic data was acquired because further in the manuscript there are ambiguities that linked to this description required at the beginning.
2. It is highly recommended to include a 4D workflow to display all processing and interpretation steps.
3. There is not any geological information section while the Arab-D formation is named. It needs to be included.
4. The authors should include their findings in the abstract.
5. Please discuss about the petro-elastic model used in detail. What method employed for solid rock, dry rock, and saturated rock bulk and shear modulus including the model, equations, parameters.
6. Since there are heterogeneity within carbonate rocks, it is recommended to discuss about pore types in this reservoir and the impact on petro-elastic model.
7. There are ambiguities with using Gassmann substitution in carbonate rocks unlike the clastic rocks. Please discuss it.
8. In figure 2a what is the red curve? Also, it is suggested to redo figure 2 in a way to divide it in 3 parts. Each part should contain the well log display together with the corresponding synthetic gathers (b, c, d) for a more appropriate assessment. It could also be compared with real seismic data and in-situ scenarios (see the next comment). Please make the corrections.
9. There are totally 3 scenarios but which one is much closer to the in-situ? In-situ scenario is not modelled yet.
10. All steps of cross-equalization for seismic data calibration should be described on your dataset including phase and time matching and correcting time-variant shift.
11. Please specify whether the authors employed the 4D seismic inversion or two separate simultaneous 3D inversion (baseline and monitor) based on updating low frequency.
12. Instead of time slice better to display horizon slice in figure 4.
13. line 293 table 2.3 or table2.
14. The authors investigated the 4D signal effect on density, P_impedance, and porosity changes. However, the main part of 4D study should be dedicated to saturation and pressure changes. Hence, it is recommended to evaluate this objective more than other changes.
15. It seems authors reported all the production and injection changes within the reservoir interval between 1994 and 2014 without any analysis and did not specify the relationship between those graphs. Please discuss this part.
16. The methodology to predict maps of saturation and pressure changes need to be elaborated. Also, how to differentiate saturation and pressure changes.
17. There should be discussion section with uncertainty and limitation in this study.
18. The conclusion should be rewritten based on the revised manuscript.
19. The colour legend, axis label, and figure caption in most of the figures are not readable. It needs to be amended.
20. some reference needs to be completed and also please check if it is in accordance with the journal’s instructions.
21. The English writing should be proofread to avoid grammatical and typo errors.
Thank you for the submission.
Author Response
Please see the attachment for Author's response to the reviewer.
Author Response File: Author Response.docx
Reviewer 3 Report
The article presented a workflow for 4D study in a carbonate reservoir.
Although the subject of study is interesting, the article needs to be improved to allow the reader to perceive its real contribution to the area.
The abstract is too long and does not highlight the main points and effective contribution of the research. There are sentences here that seem incomplete, such as: "Moreover, evaluating the changes in reservoir properties over the time-lapse of 20 years of 32 production from 1994 to 2014."
In the Introduction section, the motivation and objective of the article were not clearly stated. What is the state of the art, what are the limitations, what are the contributions and originality of this research?
References to fundamental statements for the application of the article are lacking, such as: "the acoustic velocities of carbonates are insensitive to saturation and pressure changes compared to clastic reservoirs." and "In most cases, the reflectivity of a water-bearing reservoir increases with water saturation and decreases with decreasing frequency."
Acronyms are used without their meaning being explained, such as: KPSDM and LSM.
There are some statements that in my opinion do not make sense, such as: "Note that these networks are sometimes called “artificial neural networks” - in my opinion these networks are always called artificial neural networks.
Nor do I understand what the authors meant when they said: "The advantage of supervised learning is that we can interpret the output because we have determined its nature."
Sometimes authors use "in-situe" or sometimes "insitue", but the correct would be simply "in-situ". The same with "preprocessing" and "pre-processing"
It was also unclear what the practical consequence of the discrepancy observed in the production wells was: "The matching with the in-situ situation shows some discrepancy between the measured log and the log produced by the rock physics, especially in the very porous sections of the Arab -D reservoir."
I think the English is wrong in the section title: "Seismic Inversion Supervising Machine Learning Neural Network."
There is no more detailed information about the DFNN used (how many layers, what hyper-parameters are used, what is the training stop criterion?). I was also surprised by the statement that the network trained with 6 wells performed better than the network trained with 13 wells. It is a well-known fact in Machine Learning that the more data used to train a model, the more robust it becomes in terms of overfitting.
The authors state: "It was clearly shown that machine learning gave the best fitting between the predicted density and the actual density compared to the conventional method where 6 wells were used for training and validation.", but it is not clear which is the conventional method. that is being used.
The presentation of results was confusing in the "Matching of 4D Seismic Signal with Reservoir Performance" section and it was not clear that the 4D seismic data is actually matching the reservoir production data.
The conclusion is very succinct and does not highlight the most relevant and advantageous aspects of the proposed workflow.
Author Response
Please see the attachment for Author's response to the reviewer.
Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
Thanks for considering mine suggestions. I believe the manuscript has been
sufficiently improved so it can be published as it is.
Author Response
We appreciate you reading the manuscript; we have revised, checked, and corrected each and every section for English spelling. For your reference, kindly find the improved version of the paper attached.
Additionally, we made every effort to make the section you highlight as good as we possibly could. This should make things more clear for readers.
Author Response File: Author Response.docx
