Experimental study of shear and hydraulic bonding strength between casing and cement under complex temperature and pressure conditions

The cement sheath plays a vital role in preventing gas channelling. It is important to understand the interfacial bonding between the casing and cement sheath when the downhole temperature and pressure change. This paper demonstrates the results of an experimental study to investigate the effect of high temperature and high pressure and their variations on the cement sheath interfacial bonding strength (CSIBS). An experimental device was developed that is used to test the shear and hydraulic bonding strength with the method of uniaxial compression and gas channelling. The results show that both temperature and pressure have a significant influence on the CSIBS. As the curing temperature increases with a constant curing time or as the curing time increases with a constant curing temperature, the CSIBS first increases and then converges to a stable value. The casing roughness has a crucial effect on the shear bonding strength but little effect on the hydraulic bonding strength. Though the CSIBS decreases obviously with the decrease in temperature, it undergoes little change when the temperature first increases and then recovers to the initial value. When the internal casing pressure decreases to a certain value or first increases to a certain value followed by recovery to the initial state, the hydraulic bonding strength tends to be 0 MPa, which means that the interface undergoes debonding between the casing and cement.

considered and some experimental datas are acquired which is useful to study the integrity of cement sheath. However, this paper needs some modifications to publish: 1-A language polishing is recommended for this manuscript. 2-The authors should demonstrate reasons for data changes based on time, curing time, curing temperature and casing roughness. 3-The different factors considered in this manuscript should explain the operating conditions during well completions.

Review form: Reviewer 3
Is the manuscript scientifically sound in its present form? No

Recommendation?
Major revision is needed (please make suggestions in comments)

Comments to the Author(s)
The manuscript reports useful data and methodology. I suggest major revision mainly because of the many writing issues in the manuscript. The writing is problematic and is not very careful. The authors need to ask for English writing experts to help refine their paper. There are still a lot of writing issues present in the manuscript.
Remaining major issues: 1) The writing is lacking relevant discussion on related studies. There are a number of papers dedicated to studying the bonding between cement and steel materials published in other journals such as cementing and construction materials, journal of petroleum science and engineering. When discussing the results, comparative analysis between the current findings and previous findings is highly recommended. This will make the novelty of current study clear to the readers. 2) There are not many scientific explanations on the results obtained. There are many figures not not much useful discussion on them. The authors should provide insights as regard to why this and that happen? What are underlying mechanisms? Otherwise, it carries little value to the readers if they want to exploit the research results.
3) Writing contains both logic and grammar issues. It is not quite consistent. Sometimes it is clear, but sometimes it is fuzzy. 4) Roughness effect: how is the roughness defined? The definition should be given. 5) Figure 10(a): it should be mentioned that this scheme is the temperature variation scheme used in the lab tests to mimic field conditions. Incomplete list of writing errors found in the manuscript: Page 4: Lines 11-12: Plays a vital role in doing something… Lines 42-44, the sentence has grammar issues: its complex variation which….. Which is redundant. Lines 46-50, the sentence has grammar issues: bonding strength is of utmost importance… Line 54: few works were conducted to do something… Page 5: Line 9: Guo et al. (2010) investigated… Do not need to list all the authors… The same issue appears in many places throughout the manuscript. The authors need be more aware of how to cite references in the text. Line 19: developed a study… is not correct. We cannot develop study, we can do a study… Line 26-27: which affected the accuracy of test results… The writing is not clear. What affects the accuracy of test results? Line 29: A brief introduction are as follows. It should be corrected as: The structure of this paper is as follows… Line 39-47: The whole paragraph is one sentence. The authors should divide it into smaller ones, which can make the writing more concise and easy to understand. Line Page 6: Lines 21-27: Grammar issues. What do you mean "and the amount preparation for 0.5L cement slurry is shown in Table 1."? You mean the recipe of the cement slurry? Line 31: The authors may want to get professional language help from colleagues or get some professional training on technical writing. It will be really helpful for their future paper writing...

14-Feb-2020
Dear Dr Yang, The editors assigned to your paper ("Experimental study of shear and hydraulic bonding strength between casing and cement under complex temperature and pressure conditions") have now received comments from reviewers. We would like you to revise your paper in accordance with the referee and Associate Editor suggestions which can be found below (not including confidential reports to the Editor). Please note this decision does not guarantee eventual acceptance.
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Reviewers' Comments to Author:
Reviewer: 1 Comments to the Author(s) The paper is written about an important topic that required more and more works. The literature review of the paper is still weak. Major works are not reviewed by the author, for instance, the works done by other on cement interfacial strength model and measurements for instance Tabatabaei It's better that authors report raw rheology data (graphs). The authors should reprt the expansion of the steel and cement plug due to pressurization in the experiment as a benchmark. Also need to discuss the effect of pipe expansion to the high pressure.
Reviewer: 2 Comments to the Author(s) Cement sheath integrity is important to the oil and gas well. Interfacial bonding strength between cement sheath and casing and cement sheath and formation are the basic datas to study the integrity of cement sheath. Different from the current studies, this work designs an special experimental device to measure the interfacial bonding strength between casing and cement sheath under complex temperature and pressure conditions in HTHP wells. Several factors are considered and some experimental datas are acquired which is useful to study the integrity of cement sheath. However, this paper needs some modifications to publish: 1-A language polishing is recommended for this manuscript. 2-The authors should demonstrate reasons for data changes based on time, curing time, curing temperature and casing roughness. 3-The different factors considered in this manuscript should explain the operating conditions during well completions.

Reviewer: 3 Comments to the Author(s)
The manuscript reports useful data and methodology. I suggest major revision mainly because of the many writing issues in the manuscript. The writing is problematic and is not very careful. The authors need to ask for English writing experts to help refine their paper. There are still a lot of writing issues present in the manuscript.

Remaining major issues:
1) The writing is lacking relevant discussion on related studies. There are a number of papers dedicated to studying the bonding between cement and steel materials published in other journals such as cementing and construction materials, journal of petroleum science and engineering. When discussing the results, comparative analysis between the current findings and previous findings is highly recommended. This will make the novelty of current study clear to the readers. 2) There are not many scientific explanations on the results obtained. There are many figures not not much useful discussion on them. The authors should provide insights as regard to why this and that happen? What are underlying mechanisms? Otherwise, it carries little value to the readers if they want to exploit the research results.
3) Writing contains both logic and grammar issues. It is not quite consistent. Sometimes it is clear, but sometimes it is fuzzy. 4) Roughness effect: how is the roughness defined? The definition should be given. Figure 10(a): it should be mentioned that this scheme is the temperature variation scheme used in the lab tests to mimic field conditions. Incomplete list of writing errors found in the manuscript:

5)
Page 4: Lines 11-12: Plays a vital role in doing something… Lines 42-44, the sentence has grammar issues: its complex variation which….. Which is redundant. Lines 46-50, the sentence has grammar issues: bonding strength is of utmost importance… Line 54: few works were conducted to do something… Page 5: Line 9: Guo et al. (2010) investigated… Do not need to list all the authors… The same issue appears in many places throughout the manuscript. The authors need be more aware of how to cite references in the text. Line 19: developed a study… is not correct. We cannot develop study, we can do a study… Line 26-27: which affected the accuracy of test results… The writing is not clear. What affects the accuracy of test results? Line 29: A brief introduction are as follows. It should be corrected as: The structure of this paper is as follows… Line 39-47: The whole paragraph is one sentence. The authors should divide it into smaller ones, which can make the writing more concise and easy to understand. Line Page 6: Lines 21-27: Grammar issues. What do you mean "and the amount preparation for 0.5L cement slurry is shown in Table 1."? You mean the recipe of the cement slurry? Line 31: Table 1: the decimal point of a given variable should be kept the same.

Recommendation? Accept as is
Comments to the Author(s) Finally, the authors have taken serious measures to improve their manuscript. Hopefully such revision process will be helpful for them to prepare new manuscripts in the future.
One last comment: the mathematical definition of roughness is still not given in the manuscript. They should show the equation. Reference should be provided to this definition.

31-Mar-2020
Dear Dr Yang, It is a pleasure to accept your manuscript entitled "Experimental study of shear and hydraulic bonding strength between casing and cement under complex temperature and pressure conditions" in its current form for publication in Royal Society Open Science. The comments of the reviewer(s) who reviewed your manuscript are included at the foot of this letter.
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Thank you for your fine contribution. On behalf of the Editors of Royal Society Open Science, we look forward to your continued contributions to the Journal.
Kind regards, Andrew Dunn Royal Society Open Science Editorial Office Royal Society Open Science openscience@royalsociety.org on behalf of Prof R. Kerry Rowe (Subject Editor) openscience@royalsociety.org Associate Editor Comments to Author: Thank you for so positively responding to the majority of the reviewer's comments. Given the majority view is that the paper should be accepted for publication, we are glad to recommend acceptance.
Reviewer comments to Author: Reviewer: 2 Comments to the Author(s) This paper could be accepted.

Reviewer: 3
Comments to the Author(s) Finally, the authors have taken serious measures to improve their manuscript. Hopefully such revision process will be helpful for them to prepare new manuscripts in the future.
One last comment: the mathematical definition of roughness is still not given in the manuscript. They should show the equation. Reference should be provided to this definition.

Reviewer: 1
Comments to the Author(s) The comments are provided in the above sections.