A Review on Geothermal Energy and HPHT Packers for Geothermal Applications

Round 1

Reviewer 1 Report

With each passing day, the population of the world is increasing, hence, the availability of energy has to be sufficient to meet the demand of people. Energy is an essential component for prosperity, economic growth, and development and has become a basic necessity for humans, but at the same time, it has an impact on the environment. Therefore, it is believed that in the coming future renewable energy will play an important part to fulfil the energy demand. In this manuscript, this paper gives a review of the forces acting on packers, testing standards, problems encountered by a packer in the HPHT subsurface environment, and designs to overcome those problems. I am pleased to send you moderate comments. The results and theme of this paper is interesting. Generally, this manuscript makes fair impression and my recommendation is that it merits publication in this Journal, after the following major revision:

1. The detailed literature review indicates efforts made by the authors. The coherence of the related work, however, is still not clear. It may help the authors by answering the following questions: Why are these works relevant? Which specific problems were addressed? How are the previous results related with the latest work? What are the outstanding, unresolved, research issues? Which of them has been solved by the proposed study? Answering the questions leads to the novelty of the proposed work naturally. Besides, the current one is nothing but a literature review. Why their work is important comparing to previous reports? I think this is essential to keep the interest of the reader.

2. Although the results look “making sense”, the authors should dig deeper in the results by presenting some in-depth discussion, such as implications of the results, such as possible application of them.

3. Geothermal Energy is interpreted as the heat that is acquired from the earth which

can be utilized in a wide range of applications from small scale, such as for heating a

building, to large commercial scale for the production of power (electricity). The extraction of the heat from the subsurface is done by the circulation of fluid from the bottom to the surface (see [International Journal of Heat and Mass Transfer, 2019, 137:365-371]). In most cases, the fluid, which mainly consists of brine, is produced from the geothermal reservoir. At some locations either the fluid does not exist (dry rock), or the permeability (see [Powder Technology, 2019, 349:92-98]) of the formation is very low. For such situations stimulation job is performed to increase the transfer properties of the formation. Authors should introduce some related knowledge to readers. I think this is essential to keep the interest of the reader.

4. Therefore, for effective zonal isolation, different tests have been recommended on packers by ISO and API, in which V6 grade is the lowest rated and V0, which consists of a gas-tight test, is the highest rated. Packers have their limitations when exposed to an HPHT environment hence different designs to mitigate those problems have been discussed. Though most of the illustrated packers are from the HPHT oil and gas well but the packers designed by WelltecTM (Welltec Magma Packers (WMP®)) are made exclusively for geothermal well applications and have the capacity to operate at the subsurface condition of 10,000 PSI and 300°C. The authors should give some explanation on above conclusions and data.

5. Please expand the motivation, the problem context, clarify the problem description, and (if possible) add specific objectives.

6. Please, expand the conclusions in relation to the specific goals and the future work.

 

 

Author Response

Reviewer 1:

With each passing day, the population of the world is increasing, hence, the availability of energy has to be sufficient to meet the demand of people. Energy is an essential component for prosperity, economic growth, and development and has become a basic necessity for humans, but at the same time, it has an impact on the environment. Therefore, it is believed that in the coming future renewable energy will play an important part to fulfil the energy demand. In this manuscript, this paper gives a review of the forces acting on packers, testing standards, problems encountered by a packer in the HPHT subsurface environment, and designs to overcome those problems. I am pleased to send you moderate comments. The results and theme of this paper is interesting. Generally, this manuscript makes fair impression and my recommendation is that it merits publication in this Journal, after the following major revision:

1. The detailed literature review indicates efforts made by the authors. The coherence of the related work, however, is still not clear. It may help the authors by answering the following questions: Why are these works relevant? Which specific problems were addressed? How are the previous results related with the latest work? What are the outstanding, unresolved, research issues? Which of them has been solved by the proposed study? Answering the questions leads to the novelty of the proposed work naturally. Besides, the current one is nothing but a literature review. Why their work is important comparing to previous reports? I think this is essential to keep the interest of the reader.

Dear Reviewer, we have reviewed our work and improved our introduction as well as some sentences in the introduction part to strengthen the answers to your questions. In short, failure of packers in geothermal wells is becoming an increase problem as more geothermal wells are drilled and needs relibel packers. Our review is trying to answer this issue by highlighting (see our conclusions) that noi coeheren geothermal packer testing protocol exists.

2. Although the results look “making sense”, the authors should dig deeper in the results by presenting some in-depth discussion, such as implications of the results, such as possible application of them.

Dear reviewer we have expanded our tables and included for each paper we reviewed the implication of the results.

3. Geothermal Energy is interpreted as the heat that is acquired from the earth which can be utilized in a wide range of applications from small scale, such as for heating a building, to large commercial scale for the production of power (electricity). The extraction of the heat from the subsurface is done by the circulation of fluid from the bottom to the surface (see [International Journal of Heat and Mass Transfer, 2019, 137:365-371]). In most cases, the fluid, which mainly consists of brine, is produced from the geothermal reservoir. At some locations either the fluid does not exist (dry rock), or the permeability (see [Powder Technology, 2019, 349:92-98]) of the formation is very low. For such situations stimulation job is performed to increase the transfer properties of the formation. Authors should introduce some related knowledge to readers. I think this is essential to keep the interest of the reader.

Thank you for the remarks

The information has been added and can be found on Page 2, line numbers 62 to 71, and Figure 2.

4. Therefore, for effective zonal isolation, different tests have been recommended on packers by ISO and API, in which V6 grade is the lowest rated and V0, which consists of a gas-tight test, is the highest rated. Packers have their limitations when exposed to an HPHT environment hence different designs to mitigate those problems have been discussed. Though most of the illustrated packers are from the HPHT oil and gas well but the packers designed by WelltecTM (Welltec Magma Packers (WMP®)) are made exclusively for geothermal well applications and have the capacity to operate at the subsurface condition of 10,000 PSI and 300°C. The authors should give some explanation on above conclusions and data.

Thank you for the comment

A detailed explanation of the Welltec packers can be found on Page 22 and 23, Line number 657 to 686, and Table 7.

5. Please expand the motivation, the problem context, clarify the problem description, and (if possible) add specific objectives.

Thank you for the suggestion

The information has been added and can be found on Page 12 and Line number 320 to 329.

6. Please, expand the conclusions in relation to the specific goals and the future work.

Thank you for the remarks

The information has been added and can be found on Page 25 and Line number 747 to 752.

Reviewer 2 Report

The review is commendable and authors have addressed a role of packers for geothermal applications. Authors are suggested to address these recommendations to further improve the review.

1.      
This review lacks an explanation for the international audience. Add a discussion or section regarding the world’s top countries in geothermal utilization and applications.

2.       A compilation of studies related to geothermal application in the past 5 years is missing. Add more studies within the past 5 years regarding the applications, problems, and solutions of packers for geothermal purposes.

3.       Lines 16, and 25: Abbreviations are not properly defined. First, write the whole word and define the abbreviations. Consistency is needed, and make corrections throughout the study.

4.       A detailed explanation regarding the geothermal resources in the US should be added. Add a table that shows the detailed information. An example can be find from the following study; Zhu, J., Hu, K., Lu, X., Huang, X., Liu, K., & Wu, X. (2015). A review of geothermal energy resources, development, and applications in China: Current status and prospects. Energy, 93, 466-483.

5.       Add a sketch related to the problem, purpose, solutions related to the packers.

6.       The cost and time factor should also be introduced in the study.

7.       For section 7 (Testing standard for packers), add a table regarding the grading.

8.       Stretch the figures to a maximum to make it readable and presentable. Also, improve the overall resolution of all the figures especially figures 7, 8, 9, 10, 12, 14, 15, and 18.

9.       The introduction can address some papers about the role of Carbon capture and storage for geothermal purposes. The following papers can be considered:

a)       Integrated workflow in 3D geological model construction for evaluation of CO2 storage capacity of a fractured basement reservoir in Cuu Long Basin, Vietnam. International Journal of Greenhouse Gas Control, 90, 102826.

b)       Impact of a new geological modelling method on the enhancement of the CO2 storage assessment of E sequence of Nam Vang field, offshore Vietnam. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 42(12), 1499-1512.

c)       Application of robust intelligent schemes for accurate modelling interfacial tension of CO2 brine systems: Implications for structural CO2 trapping. Fuel, 319, 123821.

d)       Developing the efficiency-modeling framework to explore the potential of CO2 storage capacity of S3 reservoir, Tahe oilfield, China. Geomechanics and Geophysics for Geo-Energy and Geo-Resources, 8(4), 1-23.

e)       Exploring the power of machine learning to predict carbon dioxide trapping efficiency in saline aquifers for carbon geological storage project. Journal of Cleaner Production, 133778.

Author Response

Reviewer 2:

The review is commendable and authors have addressed a role of packers for geothermal applications. Authors are suggested to address these recommendations to further improve the review.

1. This review lacks an explanation for the international audience. Add a discussion or section regarding the world’s top countries in geothermal utilization and applications.

Thank you for the remarks

The information can be found on the following pages, line numbers, and tables

Page 7 and Line number 169 to 174, Line number 184 to 188.

Page 8, Table 3 and 4

2. A compilation of studies related to geothermal application in the past 5 years is missing. Add more studies within the past 5 years regarding the applications, problems, and solutions of packers for geothermal purposes.

Thank you for the comments

The information has been added and can be found on Page 24 and Line number 709 to 719.

3. Lines 16, and 25: Abbreviations are not properly defined. First, write the whole word and define the abbreviations. Consistency is needed, and make corrections throughout the study.

Thank you for the suggestion

The correction has been made throughout the manuscript

4. A detailed explanation regarding the geothermal resources in the US should be added. Add a table that shows the detailed information. An example can be find from the following study; Zhu, J., Hu, K., Lu, X., Huang, X., Liu, K., & Wu, X. (2015). A review of geothermal energy resources, development, and applications in China: Current status and prospects. Energy, 93, 466-483.

Thank you for the remarks

The information can be found on pages, line numbers, tables, and figure

Page 6, Line number 156 to 161

Page 7, Line number 165 to 174, Table 2 and Figure 7

5. Add a sketch related to the problem, purpose, solutions related to the packers.

Thank you for the comments

The information has been added and can be found on Page 26, 27 and 28, and, Table 8.  

6. The cost and time factor should also be introduced in the study.

Thank you for the recommendation

The scope of study is in not related to the cost or time factor of the packer. Though in some studies time factors of the packer are considered such as on

Page 17, line numbers 483 to 484.

Page 19, line numbers 572 to 575

Page 22, line numbers 665 to 675, Figure 14

7. For section 7 (Testing standard for packers), add a table regarding the grading.

Thank you for the remarks

The information can be found on page 14 and Table 5

8. Stretch the figures to a maximum to make it readable and presentable. Also, improve the overall resolution of all the figures especially figures 7, 8, 9, 10, 12, 14, 15, and 18.

Thank you for the comments

Corrections have been made accordingly

9. The introduction can address some papers about the role of Carbon capture and storage for geothermal purposes. The following papers can be considered:
10. a)Integrated workflow in 3D geological model construction for evaluation of CO2 storage capacity of a fractured basement reservoir in Cuu Long Basin, Vietnam. International Journal of Greenhouse Gas Control, 90, 102826.
11. b)Impact of a new geological modelling method on the enhancement of the CO2 storage assessment of E sequence of Nam Vang field, offshore Vietnam. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 42(12), 1499-1512.
12. c)Application of robust intelligent schemes for accurate modelling interfacial tension of CO2 brine systems: Implications for structural CO2 trapping. Fuel, 319, 123821.
13. d)Developing the efficiency-modeling framework to explore the potential of CO2 storage capacity of S3 reservoir, Tahe oilfield, China. Geomechanics and Geophysics for Geo-Energy and Geo-Resources, 8(4), 1-23.
14. e)Exploring the power of machine learning to predict carbon dioxide trapping efficiency in saline aquifers for carbon geological storage project. Journal of Cleaner Production, 133778.

 

Dear reviewer we carefully read the paper you recommended, and we could not use them for our paper as they have nothing in common with packers nor downhole components. As the recommended papers are modeling only, we see their value in future paper but, as mentioned we could not find any common ground with our current paper.

 

Reviewer 3 Report

The authors investigate the status of geothermal energy and high-pressure and high-temperature packer for geothermal. I think that the study is in principle suitable for a publication. However, I still cannot recommend a publication of the manuscript in the present state, this manuscript would benefit from the following modifications:

1. Why the packer is the only tool mentioned in this paper. As a review paper, at least a brief overview of the downhole tools which are specials for geothermal should be introduced.

 

Author Response

Reviewer 3:

The authors investigate the status of geothermal energy and high-pressure and high-temperature packer for geothermal. I think that the study is in principle suitable for a publication. However, I still cannot recommend a publication of the manuscript in the present state, this manuscript would benefit from the following modifications:

1. Why the packer is the only tool mentioned in this paper. As a review paper, at least a brief overview of the downhole tools which are specials for geothermal should be introduced.

 

Thank you for the comments

The information has been added and can be found on Page 11, Line numbers 296 to 329, and Figure 9.

Round 2

Reviewer 1 Report

It is ok.

Author Response

Thank you for your support in reviewing and helping to make our paper better.

Reviewer 2 Report

Authors have made adequate revisions.  The review is somehow an improved version. However, there are still some minor issues.

 1. Keep the same format, fonts for every table.

2. Table 6 and Table 7 should be in text format. Replace the blurred images with new tables.

 

Author Response

Authors have made adequate revisions.  The review is somehow an improved version. However, there are still some minor issues.

1. Keep the same format, fonts for every table.
2. Table 6 and Table 7 should be in text format. Replace the blurred images with new tables.

 

Thank you for the recommendation

The changes have been made accordingly in the manuscript