Study of Chemical Additives for Optimization of Binary Systems Used for Downhole Thermochemical Treatment of Heavy Oil

Round 1

Reviewer 1 Report

The authors present an interesting research work which are useful for the development of heavy oils. The content and results are good but the structure can be improved. My comments are as follows:

 

I suggest firstly introducing the “Materials and Methods” and then the “Results and discussion”, not the process how you solve the problem step by step.

The structure of the content should be adjusted. For example, the selection of the additive should be in the “Introduction”. The design of all the experiments should not be included in the “materials and method”.

 

I noticed that the delay time increases with the concentration of HMBA (Table 1). So why not try a lower contraction to extend the delay time?

 

Line 259: It is better to show the chemical formula of formalin like other materials.

 

More chemical reactions should be discussed. The chemical additives, with strong oxidizability, can oxigenize the oil components. The acid may react with the rock materials, such as carbonate. Heavy oils commonly contain organic acids, may also react with the additives. Please refer to the review paper: Qi, Yu, Cai, Chunfang, Sun, Peng, Wang, Daowei, Zhu, Hongjian, 2023. Crude oil cracking in deep reservoirs: A review of the controlling factors and estimation methods. Petroleum Science. https://doi.org/10.1016/j.petsci.2023.03.006.

Author Response

We thank the reviewer for providing comments on this manuscript. I’m consistent in my responses to account for text corrections in the manuscript.

The "Materials and Methods" sections in the manuscript were put after the "Introduction", the "Results and Discussion" section last before the "Conclusion". I agree that this is more concise.

I agree that content structure should always be structured. The materials and methods section only summarizes the technologies, equipment, and their application designation in the paper. I believe the structure left in the text in sections 2 and 3 of the manuscript looks quite logical for understanding the experimental part of the work done. If something looks inappropriate from the point of view of the reviewer, we will work on these points again.

The reviewer's claim to the conclusion that the delay time increases with increasing HMBA concentration (Table 2) is actually not true. This is evident from the thermochemical data in the HMBA experiments. The reaction delay time is always shorter when the HMBA concentration decreases.

In section 2.1 of the manuscript, all reagents used in the work with their chemical formulas were listed as suggested by the reviewer.

In the reviewer's opinion, more chemical reactions should be discussed. Yes, it is quite clear that when the reactions under consideration are introduced and initiated in an oil saturated porous medium, several reactions will predominate with the release of different products. A number of such reactions (literature data:  Qi, Yu, Cai, Chunfang, Sun, Peng, Wang, Daowei, Zhu, Hongjian, 2023. Crude oil cracking in deep reservoirs: A review of the controlling factors and estimation methods. Petroleum Science) indicated in the manuscript when describing the chemical processes. About the disadvantages of using acids in the form of initiating additives, they also wrote in the text of the manuscript.

Reviewer 2 Report

Comments for author File: Comments.pdf

Author Response

Thank you for your review of our manuscript. A lot of work and experiments have been done to provide reliable data and interpreting as possible application of the presented chemical compositions for thermochemical treatment of bottomhole formation zone on different types of reservoirs (primarily with heavy oil).

After reading your feedback, we have expanded the aspects in the text of the manuscript regarding the selection of specific salts and surfactants and their effects in reservoir conditions. The detailed description of the chemicals used and the description of the binary mixture preparation have also been expanded in the Materials and Methods section. More detailed information on conducting filtration tests on oil-saturated core models has been added. In the section "Hydrodynamic modeling" we believe that enough information has been written to describe the method of calculations, in addition, the text of the section "Results and conclusions" provides data on all parameters for calculations in the hydrodynamic model.

The elaboration of the results is further reflected in the end of the "Results and Conclusions" section with the proposed methods of injection of the selected fluids as a practical application at the well site. The possibility of application to different fields is not given here, but we also noted that the effectiveness of the selected technologies will be influenced by a combination of factors.

Since the reviewer noted that the "Conclusions" section does not contain any analysis with previous studies in this area, it should be kept in mind that we are studying a specific binary system and its suitability for processing in the described Russian regions with given reservoir temperatures, pressures and rock type. Therefore, we do not try to compare the uniqueness of the methodology of injection of binary mixture and initiating additives with other studies. The contribution of studying the above filtration experiments in porous medium is really significant for the field of predicting the real thermobaric behavior during initiation of such reactions in order to successfully treat the bottomhole zone and reduce accident risks due to uncontrolled reactions in tubing, etc.

All other suggestions for improving the understanding of this manuscript will also be considered in each letter.

Round 2

Reviewer 1 Report

The revised paper is much better. Some minor modifications are needed. 

(1)  Line 55 misses the number order of formula?

(2)  Table 2: the units are duplicate.

(3) The main content includes "wt.%", "wt%", "%wt" and "%wt.", please unify them.

(4) Check the days-1 in Line 332.

(5) Check the authorlist of the last reference. 

Author Response

Thanks to the reviewer for last review of our manuscript. In accordance with his comments, the following changes were made:

1) The numbering order of formulas in the manuscript has been corrected, starting with formula 1;

2) Table 2 has an extra row removed, so the Table looks logical;

3) Reagent concentrations corrected to the same %wt everywhere;

4) Rate constant notation changed to correct day^-1;

5) In the last reference of the manuscript, all authors are listed according to journal norms.