Scaling Torsional Drilling Vibrations: A Simulation-Based Comparison of Downscale and Upscale Drill Strings Under Varying Torque Conditions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors conducted comparative simulations for two scaled drill string models (upscale and downscale) subjected to different torque conditions. The main goal was to understand the mechanism of torsional vibrations and stick-slip phenomenon in both configurations. The simulations included dynamic analysis at three different torque levels, which allowed to determine the effect of scaling on operational stability. The article addresses the important problem of torsional vibrations in drilling operations, which are of great importance for the oil and gas industry, comparing upscale and downscale models in terms of their dynamic behavior at different torques is an interesting research perspective. The authors used advanced simulation models, including rigid-lacing drill string models, which allows for realistic representation of real conditions. Regarding the possibilities for improving the article: The literature review is insufficient, especially in the context of the comparative nature of the study. The following is missing: - A clear summary of previous studies on the effect of scaling on torsional vibrations. - Analysis of research gaps that would justify the choice of this research approach. - In-depth reference to simulation methods used in the past. Remarks on numerical analysis - There is a lack of detailed description of the simulation software used and calibration of model parameters. - No sensitivity analysis was performed, which limits the possibility of assessing the impact of uncertainty in input parameters on the results. - The comparison of stick-slip vibration time occurrence is limited and does not take into account the influence of differences in materials or boundary conditions. - The conclusions presented in the article are poorly developed and not fully based on the obtained results. The authors only superficially analyze the significance of differences in the stability of upscale and downscale systems. - There is no explanation why upscale shows earlier vibrations at higher torques. - A deeper analysis of the physical mechanisms leading to differences in vibration amplitudes in both models. It is recommended to include the latest research on drill string dynamics and torsional vibration modeling.

Author Response

Reviewer #1: The authors conducted comparative simulations for two scaled drill string models (upscale and downscale) subjected to different torque conditions. The main goal was to understand the mechanism of torsional vibrations and stick-slip phenomenon in both configurations. The simulations included dynamic analysis at three different torque levels, which allowed to determine the effect of scaling on operational stability. The article addresses the important problem of torsional vibrations in drilling operations, which are of great importance for the oil and gas industry, comparing upscale and downscale models in terms of their dynamic behavior at different torques is an interesting research perspective. The authors used advanced simulation models, including rigid-lacing drill string models, which allows for realistic representation of real conditions. Regarding the possibilities for improving the article: The literature review is insufficient, especially in the context of the comparative nature of the study. The following is missing: - A clear summary of previous studies on the effect of scaling on torsional vibrations. - Analysis of research gaps that would justify the choice of this research approach. - In-depth reference to simulation methods used in the past. Remarks on numerical analysis - There is a lack of detailed description of the simulation software used and calibration of model parameters. - No sensitivity analysis was performed, which limits the possibility of assessing the impact of uncertainty in input parameters on the results. - The comparison of stick-slip vibration time occurrence is limited and does not take into account the influence of differences in materials or boundary conditions. - The conclusions presented in the article are poorly developed and not fully based on the obtained results. The authors only superficially analyze the significance of differences in the stability of upscale and downscale systems. - There is no explanation why upscale shows earlier vibrations at higher torques. - A deeper analysis of the physical mechanisms leading to differences in vibration amplitudes in both models. It is recommended to include the latest research on drill string dynamics and torsional vibration modeling.

 

Response to Reviewer #1

Thank you for your interest and recommendations which have improved the quality of our work (Newly added text or change of text were highlighted in yellow in the revised manuscript).

 

Issue 1: The literature review is insufficient, especially in the context of the comparative nature of the study.

 

Response: Thank you for your valuable feedback. We have revised the literature review section of our manuscript to fully capture the objectives of the study. This have been shown in the manuscript from line 42 – 96.

 

Issue 2: The following is missing: A clear summary of previous studies on the effect of scaling on torsional vibrations. Analysis of research gaps that would justify the choice of this research approach. Analysis of research gaps that would justify the choice of this research approach.

 

Response: Thank you for your insightful comment. We have reviewed and revised the manuscript to provide a detailed explanation of the research gap in this study. This can be seen in the manuscript from Line 97 – 109.

 

Issue 3: In-depth reference to simulation methods used in the past. Remarks on numerical analysis - There is a lack of detailed description of the simulation software used and calibration of model parameters. - No sensitivity analysis was performed, which limits the possibility of assessing the impact of uncertainty in input parameters on the results.

 

Response: Thank you for your clarification. We have reviewed and revised our manuscript to address this remark. The results show a sensitivity analysis which shows the effect of variations in rotational speed (RPM) and applied torque on the stick-slip severity. The results indicated that an increase in torque led to an increased in stick-slip amplitude. We also have added a description of the simulator to the manuscript

In line 115 t0 120 and in the acknowledgement section.

 

Issue 4: The comparison of stick-slip vibration time occurrence is limited and does not take into account the influence of differences in materials or boundary conditions.

 

Response: We appreciate the reviewer’s feedback on the consideration of material behavior and boundary conditions. Our study primarily focuses on the comparative analysis of stick-slip vibration occurrence between upscale and downscale drill strings under varying torque conditions. While we acknowledge that material properties can influence vibration characteristics, our model does not explicitly incorporate material behavior as a variable, as the objective is to analyze torsional response under consistent geometric and operational conditions. Regarding boundary conditions, these have been clearly defined and remain consistent throughout the simulations to ensure a controlled comparison. The specified boundary conditions are detailed in Table 1.

 

Issue 5: The conclusions presented in the article are poorly developed and not fully based on the obtained results. The authors only superficially analyze the significance of differences in the stability of upscale and downscale systems. There is no explanation why upscale shows earlier vibrations at higher torques.

 

Response: Thank you for your response. We have revised our conclusions according to these remarks. This can be seen in the manuscript from line 370 to 386.

 

Issue 6: A deeper analysis of the physical mechanisms leading to differences in vibration amplitudes in both models. It is recommended to include the latest research on drill string dynamics and torsional vibration modeling.

 

Response: We appreciate the reviewer’s suggestion regarding a deeper analysis of the physical mechanisms influencing vibration amplitudes in both models. However, our study is primarily focused on the comparative assessment of stick-slip occurrence between upscale and downscale drill strings under varying torque conditions, rather than a detailed investigation into the underlying physical mechanisms governing amplitude differences. While we acknowledge that such an analysis would provide additional insights, it falls outside the specific scope of this research, but it will be added in our future work. Additionally, we have revised our manuscript to tailor the latest research and torsional vibration modeling in line 70 to 97.

Reviewer 2 Report

Comments and Suggestions for Authors

Authors presented the simulation work on down and upscale drilling strings varying torque and their driving vibration effects.  Following suggests can be incorporated in the revision of this manuscript for better presentation.

1. Abstract is concise, will be better by adding testing rage and observed results number with error bars

2.  What is the commercial tool and related equations and details of the parameters and variables in those equations should be given either supporting or in the main paper. Mention the simulation tool version and license details in the Data availability declaration section.

3.  Quality of the figures can be improved significantly.  Merge related figures by showing different color or place them as sub figures a, b, and c.  like Figure 4, 5 and 6 because these are at different kgfm. 

4.  What is the point in showing -ve rotation speed before fluctuations  in the initial time?

5.  What is the reason for testing upscale and down scales 3x increasing ? Why not use variable like sets to highlight the importance of torque control?

 

 

Comments on the Quality of English Language

Presenting quality can be improved by writing in the comparison manner. 

Author Response

Reviewer #2: Authors presented the simulation work on down and upscale drilling strings varying torque and their driving vibration effects.  Following suggests can be incorporated in the revision of this manuscript for better presentation.

1. Abstract is concise, will be better by adding testing rage and observed results number with error bars
2.  What is the commercial tool and related equations and details of the parameters and variables in those equations should be given either supporting or in the main paper. Mention the simulation tool version and license details in the Data availability declaration section.
3.  Quality of the figures can be improved significantly.  Merge related figures by showing different color or place them as sub figures a, b, and c.  like Figure 4, 5 and 6 because these are at different kgfm. 
4.  What is the point in showing -ve rotation speed before fluctuations  in the initial time?
5.  What is the reason for testing upscale and down scales 3x increasing ? Why not use variable like sets to highlight the importance of torque control?

 

Response to Reviewer #2

Thank you for your interest and recommendations which have improved the quality of our work (Newly added text or change of text were highlighted in yellow in the revised manuscript).

 

Issue 1: Abstract is concise, will be better by adding testing rage and observed results number with error bars

 

Response: Thank you for your remark. We have revised our abstract to fully cover the objectives and results from the study. This can be seen in the revised manuscript from line 7 to 27.

 

Issue 2: What is the commercial tool and related equations and details of the parameters and variables in those equations should be given either supporting or in the main paper. Mention the simulation tool version and license details in the Data availability declaration section.

 

Response: Thank you for your response. We have added the simulator used for this study (Line 115). However, our study does not consider the background equations running within the simulator, as they are proprietary and not publicly disclosed by the software provider. Instead, we have focused on the input parameters, boundary conditions, and the interpretation of the results obtained from the simulations that can be found in Table 1 in the revised manuscript. To ensure transparency, we have provided a detailed explanation of the key parameters and variables used in the study, along with their influence on the observed trends. Also, we acknowledge the simulator we used in the acknowledgment section.

 

Issue 3: Quality of the figures can be improved significantly.  Merge related figures by showing different color or place them as sub figures a, b, and c.  like Figure 4, 5 and 6 because these are at different kgfm. 

 

Response: Thank you for your feedback. We appreciate the suggestion to improve the quality of the figures and to merge related ones with better clarity. Our reason for merging figures for top RPM and bottom RPM (upscale and downscale) was to provide a clear comparison of the string performance in both cases relative to the top RPM.

 

Issue 4: What is the point in showing -ve rotation speed before fluctuations  in the initial time?

 

Response: Thank you for your feedback. We have revised the figure to remove the negative RPM, as any negative value in this context will be considered as 0 RPM as shown from figure 2 to 10. This adjustment ensures clearer representation of the drill string’s initial conditions before fluctuations occur. We appreciate your suggestion to improve the clarity of our results.

 

Issue 5: What is the reason for testing upscale and down scales 3x increasing ? Why not use variable like sets to highlight the importance of torque control?

 

Response: Thank you for your insightful comment. The upscale string represents a conventional drill string used in oil and gas drilling, while the downscale string is a small-scale laboratory model designed to replicate similar dynamic behavior under controlled conditions. The choice of testing with a 3x increasing torque was made to systematically observe the progressive impact of torque variations on both string sizes and to ensure a consistent comparative framework between the two models as highlighted in line 119 to 122. This approach allows us to assess how each system transitions into stick-slip under increasing loads. While using variable torque sets could provide additional insights into torque control strategies, our study primarily focuses on the comparative behavior of upscale and downscale strings under controlled torque increments. Future studies could explore more complex torque variations to further analyze real-time torque management in drilling operations.

Reviewer 3 Report

Comments and Suggestions for Authors

I read this ms with some interest. While this work may be interesting, but it requires significant revision and further review. My comments are copied below:

 

• How do varying torque levels specifically affect the onset and severity of stick-slip oscillations in upscale vs. downscale drill strings, and what underlying factors contribute to the earlier onset in the upscale string?

• What role does the reduced inertia in downscale drill strings play in their heightened sensitivity to torsional vibrations, and how can this sensitivity be mitigated in practical drilling operations?

• Given the observation that increased torque compromises stability across both scales, what strategies can be employed to optimize torque management and reduce the risk of torsional instability during drilling operations?

• What are the long-term effects of sustained stick-slip oscillations on drill string integrity, and how can real-time monitoring and control systems be implemented to detect and prevent these oscillations before they cause significant damage?

• How can drilling systems with high rotational inertia be optimized to prevent early onset of stick-slip, particularly when operating at deeper depths or higher torque levels, where the risk of instability is greater?

 

Author Response

Reviewer #3: I read this ms with some interest. While this work may be interesting, but it requires significant revision and further review. My comments are copied below:

1. How do varying torque levels specifically affect the onset and severity of stick-slip oscillations in upscale vs. downscale drill strings, and what underlying factors contribute to the earlier onset in the upscale string?
2. What role does the reduced inertia in downscale drill strings play in their heightened sensitivity to torsional vibrations, and how can this sensitivity be mitigated in practical drilling operations?
3. Given the observation that increased torque compromises stability across both scales, what strategies can be employed to optimize torque management and reduce the risk of torsional instability during drilling operations?
4. What are the long-term effects of sustained stick-slip oscillations on drill string integrity, and how can real-time monitoring and control systems be implemented to detect and prevent these oscillations before they cause significant damage?
5. How can drilling systems with high rotational inertia be optimized to prevent early onset of stick-slip, particularly when operating at deeper depths or higher torque levels, where the risk of instability is greater?

 

Response to Reviewer #3

Thank you for your interest and recommendations which have improved the quality of our work (Newly added text or change of text were highlighted in yellow in the revised manuscript).

 

Issue 1: How do varying torque levels specifically affect the onset and severity of stick-slip oscillations in upscale vs. downscale drill strings, and what underlying factors contribute to the earlier onset in the upscale string?

 

Response: Thank you for your response. As shown in the results from figure 2 – 10, Varying torque levels significantly impact the onset and severity of stick-slip oscillations, with higher torque levels generally leading to increased torsional instability. In the upscale drill string, stick-slip occurs earlier due to its larger rotational inertia, which stores more energy and amplifies the oscillations when torque is applied. The higher mass and length of the upscale string also contributes to greater elastic deformation and delayed damping effects. Conversely, in the downscale string, lower inertia and stiffness result in faster but less severe oscillations.

 

Issue 2: What role does the reduced inertia in downscale drill strings play in their heightened sensitivity to torsional vibrations, and how can this sensitivity be mitigated in practical drilling operations?

 

Response: Thank you for your response. The reduced inertia of the downscale drill string makes it more sensitive to torsional vibrations because it has less rotational resistance, causing rapid oscillations when torque is applied. This sensitivity can be mitigated through techniques such as adjusting the weight on bit (WOB) to balance torque application, using torsional dampers to absorb excessive vibrations.

 

Issue 3: Given the observation that increased torque compromises stability across both scales, what strategies can be employed to optimize torque management and reduce the risk of torsional instability during drilling operations?

 

Response: Thank you for your response. To optimize torque management, we can apply real-time monitoring of torque-on-bit (TOB) and adjusting input torque dynamically based on oscillation feedback or carefully selecting WOB and RPM to minimize resonance effects and avoid critical vibration modes.

 

Issue 4: What are the long-term effects of sustained stick-slip oscillations on drill string integrity, and how can real-time monitoring and control systems be implemented to detect and prevent these oscillations before they cause significant damage?

 

Response: Thank you for your review. Real-time monitoring systems using downhole sensors can detect stick-slip patterns. Implementing predictive control algorithms can then adjust drilling parameters in real-time to suppress oscillations before they escalate. However, this will be covered in our next research.

 

Issue 5: How can drilling systems with high rotational inertia be optimized to prevent early onset of stick-slip, particularly when operating at deeper depths or higher torque levels, where the risk of instability is greater?

 

Response: Thank you for your feedback. This can be achieved by slowly increasing torque instead of applying abrupt torque changes to minimize sudden oscillations.

 

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,
Having reviewed your revised manuscript and the detailed responses to my comments, I am satisfied that all my concerns have been adequately addressed. You have successfully improved the manuscript by:

• Strengthening the literature review section with comprehensive content (lines 42-96)
• Clearly identifying and justifying the research gaps (lines 97-109)
• Including details about the simulation software and adding sensitivity analysis for RPM and torque variations
• Providing clear explanation regarding the boundary conditions and scope limitations for material properties analysis
• Developing more robust conclusions (lines 370-386)
• Incorporating recent research references (lines 70-97), while acknowledging that detailed physical mechanisms analysis will be addressed in future work

The manuscript has been significantly improved and now meets publication standards. I recommend accepting it for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

Significant improved of introduction and conclusion part. Check the references format. 

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have adequately addressed all of my previous comments and made the necessary revisions. After reviewing the updated manuscript, I find that it may now be suitable for possible publication, as the issues I raised have been resolved. At this stage, I have no further comments or concerns regarding the content.

Comments on the Quality of English Language

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