Study on Explosive Fracturing Mechanism of Qianjiang Shale Oil

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The introduction should provide an overview of works devoted to the given issue, specifying the knowledge gap and the way in which the submitted article will at least partially fill it, i.e. setting the goals. This article lacks this part and it is necessary to fundamentally revise this part.
The second chapter should contain a clear plan of experimental research, instead, it begins with a description of the details of numerical modelling. Therefore, it is necessary to supplement it with a clear description of the methods for achieving the set goals and the tools used.
Chapter 2 already contains partial research results, e.g., in Fig. 2 to 4, so revising chapters 2 and 3 into a common whole is necessary.
The formatting of citations in the text does not follow the journal standards. The numbering of equations is also not formally correct.
In the list at the end of the article, the abbreviation DEGEN is given, in the text it is DEGDN. Moreover, the list is incomplete, e.g. DFT, CHON, RHT, LS-DYNA are missing.
Chapter 5 Patents is empty.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The reviewed paper investigates the explosive fracturing technology as a method for shale oil extraction from the Qianjiang Depression formation in China. It uses ANSYS LS-DYNA numerical modeling to analyze the effects of different explosion parameters on fracturing efficiency and oil recovery. Different explosives with different oxygen balance (NTNMT, DEGDN, TNT) are analyzed to evaluate their effects on fracture propagation and potential environmental pollution. DFT (density functional theory) studies analyze the degradation processes of these explosives in contact with reservoir rocks. The aim is to find the optimal solution that maximizes oil recovery while minimizing the negative impact on the environment. The results indicate that NTNMT with positive oxygen balance shows promising properties in terms of efficiency and biodegradability.

Even though the work is strictly numerical in nature and uses only computer simulations, it is very interesting and in my opinion after changes it should be published.

 Additional questions and comments:

1. The main objection is the lack of comparison of simulation calculations to any experiment and the lack of verification of these calculations. The wave created from the explosion always propagates in all directions. The authors consider the model as a slide (2D), so the wave propagates only in two directions? Does this have any reference to real situation?
2. Please present the real mesh and dimensions of the lagrangian and eulerian models. Could you explain where is defined the air at the beginning in your model?
3. How the authors homogenized the behaviour of shale? It is composed of “albite (69.37%), dolomite (9.78%), illite (8.27%), and calcite (6.89%)”.
4. Please add a coordinate system in Figure 1. In line 146 the authors refer to the Z direction, which is perpendicular to the plane.
5. Please explain what is the source of the data (points) in Fig. 2-4?
6. In my opinion figs 7 and 8 are not to informative. Maybe lover number of points should be considered? What is the real reason of this vibrations?
7. The legends on all figures from fig. 9 are invisible and illegible.
8. Why in the middle of the patch (fig. 9) there is the square hole. Are You sure there are non-reflecting boundary conditions on the perimeter? Why these failure patterns are so asymmetric?
9. Please consider including full material cards (*.k) in consistent units in your supplementary materials - this will increase the number of references to this article after publication

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This article primarily focuses on advancements in oil extraction technology, considering both technological and environmental perspectives. Utilizing numerical modeling, the authors aim to optimize the role of explosions in enhancing the oil extraction process from oil shales. The increase in rock mass porosity, attributed to the formation of additional fractures, may significantly enhance the efficiency of the extraction process. This is an important issue for oil extraction industry, and used in practice, so deeper understanding of this phenomena is interesting.
To examine fracturing mechanism, they analyze geomechanical properties of rocks modelled as a shale rock mass, using empirical and theoretical Hoek&Brown (besides Mohr-Coulomb criterion) failure criterion, which additionally may be related to the D parameters, defining rate of disturbance of the rock-mass due to use of explosives and also quality of the rock-mass. 
One can recognize new knowledge regarding chemical and thermodynamical reactions of the explosives and their role for explosive effectiveness, linking rock stress-strain characteristics with oxygen balance in explosives dynamic reaction and gas pressure generated in blasting. 
•    In the extra suggested paragraph it should discussed in detail a range of variation of the possible results regarding the creation of new fractures, particularly because explosion reactions in rocks are generally very differentiated as a rule. 
•    This is not a consecutive analysis but many different approaches that make it difficult following the general process of interpretation. The content of the conclusions is rather poor, as compared to the multitude of formulas, parameters assumed as average numbers, particularly within the first part of the manuscript. Actually, in conclusion there is nothing about fracturing, which is emphasized in the title, but rather environmentally aspect. It would be interesting some information on percentage or volumetric increase of new space (fractures).
•    Table 1 does not contain compressive strength but there is a relation between minor and major stresses in this failure criterion. 
Nevertheless, the new results as an added value are rather informative, explaining in more detail relations interaction between rocks and explosives, then indications for technology for practical utilization, including data illustrated in the figures. The bibliography is well related to the topics discussed. 
In my opinion, despite some simplifications applied in the analysis and flaws, the article is worth publishing carrying many interesting relations explained qualitatively for research.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have carefully revised the article to eliminate the shortcomings and ambiguities mentioned in the reviews. In this form, the article is ready for approval and preparation for publishing.

Reviewer 2 Report

Comments and Suggestions for Authors

In my opinion the article is very good in the present form.