Study on Mechanism of Stick–Slip Vibration Based on Torque Characteristics of PDC Bit
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsQuestions and observations
1. For the sake of the readers, it is necessary to explain what is PDC?
2. 2. In the introductory part, it should be stated what kind of vibrations exist in the drilling tool? Which are the most dangerous?
3. Chapters 2 are written incorrectly (they are repeated).
4. One cannot immediately start with a table or figure under the title of a chapter or subsection (table 2 and figure 8). First you have to write the text where you refer to the table or image.
5. In Chapter 2. Materials and Methods, subsections 1.1 etc. are listed.
6. Figure 5 should be drawn in a better quality with a better representation of the torsional force. Torsional force causes sliding.
7. Change the title of chapter 2. Study on Torsion Variable Characteristics of PDC Bit Drilling Drill String, to some other number. In the following, revise the ordinal numbers of the chapters.
8. Specifying the quantities below the expression must be more transparent (two lines cannot stand).
9. Figure 11 should be modeled differently for better visibility. Instead of a linear model, perhaps a simpler volumetric model should be done. It must show the same load distribution as the line model.
10. After Figure 11 (or within Figure 11), a model of the same system with the first few natural oscillations or frequencies (their modes) should be added. The first natural frequency tells us about the strength of the whole system. Dynamics best describes the state of the system.
11. Page 13, Line 212: what does the number 5200600068007600 mean?
12. In the Conclusion, generally known matters are stated. What are the directions for further research? What solutions can be given to reduce the negative impact of vibrations? How does vibration affect drilling efficiency?
Author Response
For your question, we have made targeted modifications in the article and highlighted it to make it more prominent. Please refer to the attachment
Question 1：For the sake of the readers, it is necessary to explain what is PDC?
The feedback you provided is very useful, so we have made the following modifications in the text.PDC has been introduced in the Introduction
Question 2： In the introductory part, it should be stated what kind of vibrations exist in the drilling tool? Which are the most dangerous?
The feedback you provided is very useful, so we have made the following modifications in the text.has been introduced in the Introduction
Question 3：Chapters 2 are written incorrectly (they are repeated).
The feedback you provided is very useful, so we have made the following modifications in the text.Modifications have been made
Question 4： One cannot immediately start with a table or figure under the title of a chapter or subsection (table 2 and figure 8). First you have to write the text where you refer to the table or image.
The feedback you provided is very useful, so we have made the following modifications in the text.Table 2 and Figure 8 have been re edited
Question 5： In Chapter 2. Materials and Methods, subsections 1.1 etc. are listed.
The feedback you provided is very useful, so we have made the following modifications in the text.The materials and methods have been listed in the chapter
Question 6： Figure 5 should be drawn in a better quality with a better representation of the torsional force. Torsional force causes sliding.
The feedback you provided is very useful, so we have made the following modifications in the text.Redeveloped higher quality images and replaced the images in the text
Question 7： Change the title of chapter 2. Study on Torsion Variable Characteristics of PDC Bit Drilling Drill String, to some other number. In the following, revise the ordinal numbers of the chapters.
The feedback you provided is very useful, so we have made the following modifications in the text.Chapter titles and serial numbers have been changed
Question 9-10： Figure 11 should be modeled differently for better visibility. Instead of a linear model, perhaps a simpler volumetric model should be done. It must show the same load distribution as the line model.
After Figure 11 (or within Figure 11), a model of the same system with the first few natural oscillations or frequencies (their modes) should be added. The first natural frequency tells us about the strength of the whole system. Dynamics best describes the state of the system.
Your proposal is very good and very professional, which has greatly inspired our experiment. We will further study it in future experiments
Question 11：Page 13, Line 212: what does the number 5200600068007600 mean?
The feedback you provided is very useful, so we have made the following modifications in the text.Units with missing numbers have been added again
Question 12：In the Conclusion, generally known matters are stated. What are the directions for further research? What solutions can be given to reduce the negative impact of vibrations? How does vibration affect drilling efficiency?
The feedback you provided is very useful, so we have made the following modifications in the text.How to reduce the impact of vibration has been added to the conclusion (Conclusion 5)
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsReviewer strongly suggests to add the Nomenclature and acronyms.
The quality English in this paper needs to be improved.
Please enter the rotational speed unit in [rpm] (instead of [r/min]).
Please correct your conclusions because it is hard to believe that: "The working torque of PDC bit has... great influence on ... rock strength...".
Comments on the Quality of English LanguageThe quality English in this paper needs to be improved. In many places in the text, there is a lack of punctuation marks and some sentences and phrases are incomprehensible.
Author Response
Comments:
Reviewer strongly suggests to add the Nomenclature and acronyms.
The quality English in this paper needs to be improved.
Please enter the rotational speed unit in [rpm] (instead of [r/min]).
Please correct your conclusions because it is hard to believe that: "The working torque of PDC bit has... great influence on ... rock strength...".
The feedback you provided is very useful, so we have made the following modifications in the text.We have improved the English proficiency of the article and made many corrections to its issues.We have replaced [r/min] in the text with [rpm].The conclusion in the article was expressed incorrectly and has now been revised to make it more accurate.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsDear Authors,
This was a very interesting read, however it seems some issues require a little more explaining. The details are given in the form of comments in the body of the PDF file attached. I strongly encourage you to consider some further study of the single cutting edge - rock block interaction. Such a study could be later developped into a credible model of the behaviour of the full PDC drilling bit at normal operational conditions.
Best of luck in your further exploits!
Your reviewer.
Comments for author File: Comments.pdf
There is most likely a misunderstanding of the word 'viscous' and 'viscosity'. That issue must be corrected.
Also the use of term 'energy' instead of 'torque' is a flaw.
Detailed commentry is given in the PDF.
Author Response
comment ：
Is this axis expressing the cutting depth per tooth, as seems to be mentioned in verses 48 and 49 ? Otherwise the magnitude of this parameter does not match the images of the holes drilled during the course of the experiment, as presented in Figure 2.
response：
This axis indicates the depth of cut for each tooth
comment ：
In real-life wellbore operations the lenght of the piping which forms the bore's body can be hundreds of meters long. In our test rig there seems to only be a very short secton of the drill piping connecting the drive system and the drill bit. Has the torsional flexibility of the drill pipe been simulated in any way? If yes, how? If not, how do your results compare to real wellbore conditions?
response：
Sensors were installed at the end of the drill string in the experimental test system, and the three-way acceleration, especially the circumferential torsion, was measured, and the results were calibrated and verified.
comment ：
0.25mm、0.50mm、0.75mm、1.00mm、1.25mm、1.50mm、2.00mm、2.50mm、3.00mm these penetration depths need explaining for reasons mentioned eariler in this series of review comments.
response：
According to the actual drilling conditions, the ROP of high-hardness formations is less than 1 meter, and the ROP of medium-hard and above formations can reach more than 10 meters.
comment ：
Is this the torsional deformation of the drill column?
How is such a large torsional deformation achieved in your test rig? Is there an element of adjustable torsional rigidity installed?
response：
This is the result of a simulation analysis where the torsion variable is within reasonable limits for several kilometre drill string lengths.
comment ：
1000 m long drill pipe as an example
response：
This is the result of the simulation analysis
comment ：
Do I understand correctly that the parameter you call either the 'penetration depth' or the 'intrusion depth' is, in fact, the feed rate of the drill bit in to the rock block per unit time?
response：
The intrusion depth is the amount of footage that the drill bit rotates in one turn.
comment ：
Is there, perhaps, any study on this particullar characteristics of the interaction between a single cutting edge (as used in the PDC bits) and the standard rock blocks? Cutting resistance vs cutting velocity at various feed rates? Such a study could form a nice foundation for some serious modelling of the full drill bit and rock block interaction.
response：
Our team has been carrying out long-term research on the rock breaking mechanism and cutting mechanics of the interaction between PDC drill bits and rocks, and established a calculation model for cutting mechanics considering the influencing factors such as rock strength, tooth profile characteristics, working parameters, etc., which form a supporting role for this paper.
comment ：
How do you the relationship between that parameter in simulation and the experiments performed? It does not seem to be an obvious thing when studying the photograph of the test rig presented in figure 2
response：
The experimental tests mainly carry out the influence relationship between drilling pressure and torque and drilling speed under different working conditions, and these experimental results provide a supporting basis for calculating the boundary conditions of the simulation analysis of the drill string system. The results of the interaction between the drill bit and the rock are mainly obtained by experiments, and the analysis of the torsional characteristics of the drill string is mainly obtained by simulation analysis.
comment ：
Is there any consideration of the friction at the sides of the drill string? There are some viscous effects present, which will cause vibration damping.
If not, there seems to be the possibility to actually simplify this system to the form of a single mass and single stiffness set in sliding motion. That is, if the resistance characteristics with respect to normal load and cutting velocity are known.
response：
The influence of friction and damping on the torsion of the drill string was not considered in this paper, and it was gradually improved in the follow-up research work.
comment ：
1. The instinctive reasoning here would rather indicate the maximum loading on the cutting teeth to occur right before the end of the stick phase, when the drill string is subjected to maximum torsional deformation.
2. The end of the slippage phase is likely to take place when the elastic energy has been released and while the cutting process is stable, causing a gradual deceleration of the rotational movement of the PDC tip.
3. On the one hand, the moment at which the cutting stops can cause some dynamic spike of the loading at the cutting teeth, but on the other hand that might be happening when the torsional deformation of the drill string is reversed or zero, so the terminal torque of the cycle (right before the end of the slippage phase) might not be the greatest.
4. The two figures: 13 and 14 should be brought together for easier reception.
5. The initial 10 seconds of the simulation are the startup of the drilling, while the stick-slip is observed when the rotational speed of the turntable and the axial load on the drill are at nominal. That part is of little relevance to the actual study.
response：
I would like to thank the reviewers and editors-in-chief for their hard work in reviewing this paper, and the professional ability and academic height of the reviewers have played a key role in the further improvement of the academic level of this paper.
Fig. 13 is an analysis of the change of rotational speed near the drill bit, and Fig. 14 is an analysis of the change of torque at different drill pipes. There are certain differences between the two needles, and the author believes that it is more beneficial for readers to read and understand the analysis separately.
comment ：
Why? Is the fricton against the hole sides taken into consideration? I have not noticed any mention of such approach. Instead, it seems the consideration is all about a flexible, tubular drill string with the PDC bit at the bottom of the drill hole. At static conditions, with no vibrations, the torque is constant over the entire length of the drill string.
response：
In this paper, the influence of the friction between the drill string and the borehole wall on the torsional deformation is not considered. The main research in this paper is based on the influence of torque fluctuation caused by the change of the drill bit on the torsional variable of the drill string due to the change of the penetration depth of the drill bit into the bottom hole, and then the mechanism and preventive measures of stick-slip vibration are studied.
comment ：
The drill string will accumulate the energy of the rotational deformation if there is the sticking phase present at the PDC bit and the turntable is running, but it will be the torque buildup at the PDC-rock blocko contact, which will eventually break the blockage.
response：
You're right
the another issue Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe paper represents a contribution to the research of the topic.
Continue with research.
Author Response
comment：
The paper represents a contribution to the research of the topic.
Continue with research.
ressponse：
Thank you for your acknowledgment of the article, and we will conduct further research on the project
Reviewer 2 Report
Comments and Suggestions for AuthorsAs in previous case reviewer strongly suggests to add the Nomenclature and acronyms.
Author Response
comments：As in previous case reviewer strongly suggests to add the Nomenclature and acronyms.
resspone：
Thank you for your comments, your suggestion is very effective and after consideration we have revised the Stick-slip Vibration in the article using the acronym to SSV
Author Response File: Author Response.pdf
