Dynamically Coupled Reservoir and Wellbore Simulation Research in Two-Phase Flow Systems: A Critical Review

Round 1

Reviewer 1 Report

The manuscript includes a relevant area of study and relevant process used in the oil and gas industry; however, it needs to be reviewed so that the rationale and research gaps are well identified.

In term of the structure of the manuscript, the current version is difficult to follow as is not well structured. Specifically, some important definitions of process and relevant variables are mentioned but not defined and then included later in section 3).

Although the manuscript includes relevant findings from existing publications as part of a research review, it lacks originality and critical analysis of relevant findings with clear explanation of the limitation of existing models, which will be part of the original contribution to knowledge.

The referencing method used is mixed as some citations from figures have been included as numbers and some as Harvard method.

There is an existing similar review (identical area) which includes relevant findings and similar figures 1, 2 and table 3. Review publication entitled "A Review of Coupled Dynamic Well-Reservoir Simulation"-D. V. A. da Silva et al. / IFAC-PapersOnLine 48-6 (2015) 236–241.

There are not relevant conclusions from the study and discussion of findings, instead is a summary which some repetition of basic principles of simulation.

 

In general, the manuscript should include more current publications (2015-2022) considering there is a review published in 2015. 

The manuscript also needs to be proofreading checked.

 

Author Response

List of Responses

Dear editors and reviewers:

Thank you for your comments concerning our manuscript entitled “Dynamically Coupled Reservoir and Wellbore Simulation Research: A Critical Review”. These comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made corrections which we hope meet with approval. Revised portions are marked in red on the paper. The main corrections in the paper and the responses to the reviewer’s comments are as follows:

 

Reviewer: 1
Comments to the Author
The manuscript includes a relevant area of study and relevant process used in the oil and gas industry; however, it needs to be reviewed so that the rationale and research gaps are well identified.

 

In term of the structure of the manuscript, the current version is difficult to follow as is not well structured. Specifically, some important definitions of process and relevant variables are mentioned but not defined and then included later in section 3).

Response: The authors have incorporated more equations about energy balance and defined all the mentioned variables in section 3. More details are provided to better understand the numerical implementation of the coupling system. We reorganize the introduction and rewrite the summary to make this manuscript more readable.

 

Although the manuscript includes relevant findings from existing publications as part of a research review, it lacks originality and critical analysis of relevant findings with clear explanation of the limitation of existing models, which will be part of the original contribution to knowledge.

Response: In the conclusion, we discuss the existing coupled models and emphasize the future development in this research field.

 

The referencing method used is mixed as some citations from figures have been included as numbers and some as Harvard method.

Response: The authors updated the figure citation style to conform to the Harvard system.

 

There is an existing similar review (identical area) which includes relevant findings and similar figures 1, 2 and table 3. Review publication entitled "A Review of Coupled Dynamic Well-Reservoir Simulation"-D. V. A. da Silva et al. / IFAC-PapersOnLine 48-6 (2015) 236–241.

Response: Da Silva et al., 2015 authored a fantastic review in this field. The authors cited important figures and tables in their article. This study highlights the application of the DF models for coupling the wellbore system and reservoir system. Furthermore, we honor the fully implicit coupling scheme for future development to solve transient flow problems between reservoir and wellbore.

 

There are not relevant conclusions from the study and discussion of findings, instead is a summary which some repetition of basic principles of simulation.

Response: The authors updated the conclusion to provide a synopsis of the underlying mechanism of the findings mentioned.

 

In general, the manuscript should include more current publications (2015-2022) considering there is a review published in 2015.

Response: The authors include more publications in the introduction and section 3 coupled reservoir/wellbore modeling. It should be emphasized that the authors supplement those publications with fully coupled models. Semi-analytical and analytical models are not addressed.

 

Author Response File: Author Response.docx

Reviewer 2 Report

Overview of mostly isothermal two-phase flow wellbore-reservoir coupling. Title/abstract/keyword should reflect that.

Line 49:  Nennie et al. (Alberts et al., 2007): Is this reference correct? 

Line 73/74: "Coupled reservoir/wellbore simulations mean the coupling of two systems of two partial differential equations (PDEs)" Is that true that every reservoir simulator have a system of two PDE's? And two PDE's in wellbore simulator? Or you mean for two-phases systems? 

Line 195: (OGLA) -> OLGA

Table 2: Haven't described variables. 

Line 305: "The fully implicit coupling scheme requires t he most computational time among the three schemes and produces the most stable solution for a coupled reservoir/wellbore simulation because a Jacobian matrix is much larger than that for 307 independent wellbore or reservoir simulators." Stability is not related to Jacobian matrix size. Sentence needs to be rewritten. 

Line 340: It can be drawn from F igure 4 that the simulation points between the coupled reservoir/wellbore simulator and simulator MoReS are slightly different.". Does the reservoir simulator used in this paper when not coupled with the wellbore matches MoReS simulator results? Otherwise how can you trust that difference observed is about the wellbore model being added? 

Line 353: Well storage -> wellbore storage effect 

Figure 8: Does the wellbore model matches OLGA when no reservoir is coupled? 

Fig 9: Why you have chosen this time Eclipse 300? 

Fig. 10: Don't understand what Fig. 10 adds to the paper. I would not call section 4 a case study, it's just mentioned someone else did a study without any details. 

For a state-of-art paper, missed a case-study with a comparison of explicit, implicit and fully-implicit methods.

Author Response

List of Responses

Dear editors and reviewers:

Thank you for your comments concerning our manuscript entitled “Dynamically Coupled Reservoir and Wellbore Simulation Research: A Critical Review”. These comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made corrections which we hope meet with approval. Revised portions are marked in red on the paper. The main corrections in the paper and the responses to the reviewer’s comments are as follows:

 

 

Reviewer: 2

Overview of mostly isothermal two-phase flow wellbore-reservoir coupling. Title/abstract/keyword should reflect that.

Response: The authors have added the total energy balance equations in the coupled reservoir/reservoir system. Moreover, we revised the title and abstract to reflect the topic of two-phase flow.

 

Line 49:  Nennie et al. (Alberts et al., 2007): Is this reference correct?

Response: Sorry, the authors cite the wrong reference, it should be Nennie et al., 2008.

 

Line 73/74: "Coupled reservoir/wellbore simulations mean the coupling of two systems of two partial differential equations (PDEs)" Is that true that every reservoir simulator have a system of two PDE's? And two PDE's in wellbore simulator? Or you mean for two-phases systems?

Response: We modified the statement to make it more comprehensible. In reality, each reservoir simulator and wellbore simulator contains a PDEs system. Coupled reservoir/wellbore simulations involve the coupling of reservoir system and wellbore system. 

 

Line 195: (OGLA) -> OLGA

Table 2: Haven't described variables.

Response: Thanks to your thorough evaluation, we have corrected the incorrect phrasing of the OLGA simulator and expanded on the definitions of the variables in Table 2.

 

Line 305: "The fully implicit coupling scheme requires t he most computational time among the three schemes and produces the most stable solution for a coupled reservoir/wellbore simulation because a Jacobian matrix is much larger than that for 307 independent wellbore or reservoir simulators." Stability is not related to Jacobian matrix size. Sentence needs to be rewritten.

Response: The authors rewrite this sentence. The Jacobian matrix is related to the computational time but is not causally related to stability. The revised statement is as follows:

The Jacobian matrix in the fully implicit scheme is much larger than that for independent wellbore or reservoir simulators. The fully implicit coupling scheme requires the most computational time and produces the most stable solution for a coupled reservoir/wellbore simulation among these three schemes.

 

Line 340: It can be drawn from F igure 4 that the simulation points between the coupled reservoir/wellbore simulator and simulator MoReS are slightly different.". Does the reservoir simulator used in this paper when not coupled with the wellbore matches MoReS simulator results? Otherwise how can you trust that difference observed is about the wellbore model being added?

Response: In Figure 7, the coupled reservoir/wellbore simulator and reservoir simulator MoRes perform slightly different simulation results. In particular, the coupled simulator simulates a lower bottom hole pressure and an earlier gas conning time. A standalone reservoir simulator MoRes use a constant PI to simulate the gas coning phenomenon. The coupled simulator has the dynamic PI and lower bottom hole pressure, resulting in a larger mass flow and a quick gas breakthrough time. Consequently, the added wellbore model coupling the reservoir model performs different simulation results with the reservoir simulator MoRes.

Line 353: Well storage -> wellbore storage effect

Response: The authors revised related details about wellbore storage effects.

 

Figure 8: Does the wellbore model matches OLGA when no reservoir is coupled?

Response: The original authors (Nennie et al., 2008) claimed that their coupled reservoir/wellbore simulator was the coupling between reservoir simulator MoRes and wellbore simulator OLGA. Although the original authors offer no meaningful comparisons, we hypothesize that the wellbore model and simulator OLGA match well. Thanks for your question, we provide more details about the coupled reservoir/wellbore simulators in section 4.2.

 

Fig 9: Why you have chosen this time Eclipse 300?

Response: The primary reason E300 was chosen for comparison was that Shi’s DF model was applied to E300. Tang et al. modified their DF model based on Shi’s model.

 

Fig. 10: Don't understand what Fig. 10 adds to the paper. I would not call section 4 a case study, it's just mentioned someone else did a study without any details.

Response: The authors revised the portion of section 4.4. Figure 10 shows the segments of the wellbore coupling to the reservoir in complex well types. Also, “case study” is replaced with typical applications.

 

For a state-of-art paper, missed a case-study with a comparison of explicit, implicit and fully-implicit methods.

Response: In section 3.3, the authors provided further information about comparing these three coupling systems. In addition, we updated the conclusion to illustrate the coupling scheme’s future potential.

Author Response File: Author Response.docx

Reviewer 3 Report

Please consider the following items:

1- in line 195, please correct  the typo of Oil and Gas simulator (OLGA)

2-Tables and figures title's font are bold, please check with MDPI's format.

3- In line 289, (Figure 4), Please consider Pre as an input data into your flowchart

4- In line 301, (Figure 5),  if you model is not converging then what will be the next action?

5- In line 349, Please mention the ICV's flow rates in your plots?

Author Response

List of Responses

Dear editors and reviewers:

Thank you for your comments concerning our manuscript entitled “Dynamically Coupled Reservoir and Wellbore Simulation Research: A Critical Review”. These comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made corrections which we hope meet with approval. Revised portions are marked in red on the paper. The main corrections in the paper and the responses to the reviewer’s comments are as follows:

 

 

Reviewer: 3

 

1- in line 195, please correct the typo of Oil and Gas simulator (OLGA)

Response: Thanks for your thorough assessment, the authors have updated the incorrect wording of the “OLGA” simulator.

 

2-Tables and figures title's font are bold, please check with MDPI's format.

Response: We have checked the format of journal processes and revised the title of tables and figures.

 

3- In line 289, (Figure 4), Please consider Pre as an input data into your flowchart

Response: Thanks for your advice, the authors put Pre as the input data in figure 4.

 

4- In line 301, (Figure 5), if you model is not converging then what will be the next action?

Response: In fact, only after the coupled model has converged can the next time step be increased. Even if the coupled model is not converging at a certain iteration n, the new calculated reservoir pressure and Q by reservoir model will be used as the fresh input parameters to solve the wellbore model, and the iteration flowchart in Figure 5 will be repeated until the coupled model is converged. More details are described in the explanatory text of Figure 5.

 

5- In line 349, Please mention the ICV's flow rates in your plots?

Response: Thanks for your guidance, we would like to mention these three ICVs’ flow rates. However, the original authors of reference Nennie et al., 2008 do not provide exact flow rates in their paper. More details about ICV’s basic information are supplemented in the manuscript. Our objective is to demonstrate that a coupled reservoir/wellbore simulator predicts the gas coning phenomenon more precisely than a single reservoir simulator.  

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The new version of the manuscript includes most of the given feedback and has been improved.  I would recommend for publication pending few corrections in the citation method and some pending misspellings.

 

Citation: When the author of the reference is mentioned in the text, the name is not needed again in parentheses. Example:

Smith and Johnson (2018) investigated the advantages …..

Also, there were some missing corrections as follow:

Line 386   change Figure 4 by Figure 7

Line 428   change OGLA by OLGA

Lines 523, 694  correct CO2 as CO₂

Comments for author File: Comments.pdf

Author Response

Respond：Many thanks for your thorough review, we have corrected the citation  method about author in parentheses and and revised those misspellings in our manuscript.

Reviewer 2 Report

"Line 340: It can be drawn from F igure 4 that the simulation points between the coupled reservoir/wellbore simulator and simulator MoReS are slightly different.". Does the reservoir simulator used in this paper when not coupled with the wellbore matches MoReS simulator results? Otherwise how can you trust that difference observed is about the wellbore model being added?

Response: In Figure 7, the coupled reservoir/wellbore simulator and reservoir simulator MoRes perform slightly different simulation results. In particular, the coupled simulator simulates a lower bottom hole pressure and an earlier gas conning time. A standalone reservoir simulator MoRes use a constant PI to simulate the gas coning phenomenon. The coupled simulator has the dynamic PI and lower bottom hole pressure, resulting in a larger mass flow and a quick gas breakthrough time. Consequently, the added wellbore model coupling the reservoir model performs different simulation results with the reservoir simulator MoRes."

Do you use MoRes simulator to couple with a wellbore model or other simulator? If other, do they match when have same constant PI to simulate gas coning?  

Author Response

Do you use MoRes simulator to couple with a wellbore model or other simulator? If other, do they match when have same constant PI to simulate gas coning?  

Response: Sorry, the authors do not use MoRes simulator to coupe with OLGA or other wellbore simulator. The original authors Nennie et al. 2008 compared the simulation results of coupled model and single reservoir simulator MoRes. We summarized what they observed and give our explainations in this  review paper. In our future work, we will  proposed our own coupled reservoir/wellbore model to simulate the gas coning phenomenon. A standalone reservoir simulator with the constant PI will be employed  to validate our model.