Modeling Transient Flow in CO2 Injection Wells by Considering the Phase Change
Round 1
Reviewer 1 Report
The method presented by the authors seems to be well validated and agreement with experimental results is very good. It would be interesting that the authors include some information if available commercial codes could be used for this purpose.
In general, the English writing needs a good revision.
Here are some specific suggestions and comments
Line 34: replace “two theories” by “approaches”
Line 87, eq. (2): it would be interesting to have the expression for the viscous terms.
Line 99: replace “heat change caused by conduction” by “heat transfer by conduction”
Line 99: replace “heat change caused by friction” by “heat generation rate due to friction”
Iine 160: please justify why you used an explicit method, thus limiting time step, instead of an implicit method.
Please give some information regarding CPU time to perform the calculations
Author Response
The method presented by the authors seems to be well validated and agreement with experimental results is very good. It would be interesting that the authors include some information if available commercial codes could be used for this purpose.
Comment 1: In general, the English writing needs a good revision.
Response 1: Following the reviewer’s suggestion, the language expression has been edited by Elsevier Language Editing Services. No conflict of interest exists in the submission of this manuscript.
Comment 2: Line 34: replace “two theories” by “approaches”.
Response 2: Following the reviewer’s suggestion, we have replaced “two theories” by “approvals”.
Comment 3: Line 87, eq. (2): it would be interesting to have the expression for the viscous terms.
Response 3: Thanks very much for the suggestion on Eq. (2). As the reviewer said, viscosity has an impact on the flow. Actually, we have considered the viscosity of the liquid the flow. The viscosity of liquid has been taken into account in the form of friction on the pipe wall, as can be seen via the friction pressure drop in Eq. (2). This is because we used the assumption of one-dimensional flow in this paper. This assumption is valid and reasonable for the large-scale wellbore in petroleum engineering.
We feel sorry that we didn’t clarify the assumption in the previous manuscript, which may lead to the misunderstanding of readers. According to your comment, we added the assumption of one-dimensional flow in Line 74 and Line 83.
Comment 4: Line 99: replace “heat change caused by conduction” by “heat transfer by conduction”.
Response 4: Following the reviewer’s suggestion, we have replaced “heat change caused by conduction” by “heat transfer by conduction”.
Comment 5: Line 99: replace “heat change caused by friction” by “heat generation rate due to friction”.
Response 5: Following the reviewer’s suggestion, we have replaced “heat change caused by friction” by “heat generation rate due to friction”.
Comment 6: Line 160: please justify why you used an explicit method, thus limiting the time step, instead of an implicit method.
Response 6: Thanks a lot for the comment on the solution methods. As the reviewer said, there are differences between implicit and explicit methods.
For the implicit method, it allows users to use a longer time step. But the implicit approach requires the iteration method, which is more complicated than the explicit approach.
For the explicit method, the main problem could be that the small time step results in a long computation time. But, in this work, we tested several time-steps and found that it is accessible to use the explicit method. As can be seen from the solution part, the wellbore is divided into several parts axially. When the length of an individual axial part is suitable, the time step can be set with a proper value for the fast calculation. We have added the space step and time step used in this work, as can be seen from Line 168 to Line 170. It can be seen that the time is short enough to complete the calculation.
Besides, considering that the explicit approach can reach the goal of accurate calculation (which has been verified in section 3), the explicit method satisfies the goal of this work. Therefore, we adopted the explicit method in this paper.
According to the reviewer’s suggestion, we have supplemented the description of the reason why we used the explicit method, as can be seen in Line 157.
Comment 7: Please give some information regarding CPU time to perform the calculations.
Response 7: According to the review’s comment, the CPU time for calculation has been added to the paper. Please see Line 168 to Line 170.
Reviewer 2 Report
Authors study an important process from the point of view of engineering applications in petroleum industry. Application of transient flow in CO2 injection wells by considering the phase change using supercritical CO2 is a very interesting approach. However, in some points the obtained data are not well discussed or conclusions are not sufficiently justified by the content (see specific comments included in the manuscript; the proposal of remarks are introduced using the option “Comment” in PDF document).
In order to improve the quality of the paper I suggest following:
- Authors should rewrite numerous sentences and paragraphs with the help of an expert in English language and edit the whole text.
- Provide the responses for each specific comment in PDF document of the corrected manuscript.
- I have carefully checked the manuscript and I didn’t find any manuscript from Processes. This may give an impression to readers that the work is outside the scope of Processes journal, although journal publish routinely in this area. I ask that authors rework the list of references.
Author Response
Authors study an important process from the point of view of engineering applications in petroleum industry. Application of transient flow in CO2 injection wells by considering the phase change using supercritical CO2 is a very interesting approach. However, in some points the obtained data are not well discussed or conclusions are not sufficiently justified by the content (see specific comments included in the manuscript; the proposal of remarks are introduced using the option “Comment” in PDF document).
Comment 1: Authors should rewrite numerous sentences and paragraphs with the help of an expert in English language and edit the whole text.
Response 1: As the reviewer suggested, the language expression has been edited by Elsevier Language Editing Services. No conflict of interest exists in the submission of this manuscript.
Comment 2: Provide the responses for each specific comment in PDF document of the corrected manuscript.
Response 2: Thanks for your kind reminder, we have provided the responses for each specific comment in PDF document of the corrected manuscript.
Comment 3: I have carefully checked the manuscript and I didn’t find any manuscript from Processes. This may give an impression to readers that the work is outside the scope of Processes journal, although journal publish routinely in this area. I ask that authors rework the list of references.
Response 3: Following the reviewer’s suggestion, we have revised the list of references and added relevant research results from Processes.
