Vibration of Periodic Drill-Strings with Local Sources of Resonance

Round 1

Reviewer 1 Report

Dear Authors. 

Hereinafter I display my remarks. First of all: what do the red marks in the whole document mean ?

1) The paper is very inserting as it deals with vibrations in drill-strings and mitigation strategies. It is very inserting the idea of periodic inserts in the control of bending-induced vibrations. So first of all I will improve pictures in Fig. 1 and Fig. 2. Also remove the red marks in these figures' captions.

2) Figure 3 is very illustrative. Improve it, and allocate the caption in the same page.

3) Caption of Table 4 and the table are in different allocations.

4) Finite element model is correct. Is it possible to estimate the error of these models ?

5) Fig. 7 and Fig. 8 are collapsed. They have to be zoomed. Also for Figs. 11, 12 and 13. Fig. 11 caption and Fig. 11 are in different pages.

Thank you

Author Response

We appreciate very much all your constructive comments.

Attached please find the response to ALL your comments.

Author Response File: Author Response.pdf

Reviewer 2 Report

A brief summary:

In this paper the authors introduce a new class of drill-strings with periodic inserts provided with sources of local resonance (LR), to extend the bandgap characteristics to low operating frequencies and lower operating speeds. The inserts make the drill-string act as a low frequency pass mechanical filter for the transmission of vibration along the drill-string. The emphasis was placed on developing a finite element model (FEM) of this new class of drill-strings to account for the simultaneous bending, torsional, and axial vibrations. Proper design of the periodic inserts with sources of LR tend to shift these stop bands towards zones of lower frequencies to enable confining the dominant modes of vibration of the drill-string within these bands. In this manner, propagation of the vibration along the drill-string can be completely blocked. The potential application spectrum of the proposed new class of periodic drill-strings is envisioned to be beneficial to improving the quality and the state-of-the-art of drilling operations both in land and in sea.

Broad comments:

1. The outer diameter of the considered periodic inserts as well as the outer diameter of the considered periodic inserts with sources of local resonance (outer steel ring) are equal and amount to 0.2286 mm which is slightly less than the outer diameter of the drill collars 0.235 mm).
   1. Explain whether there are limitations in the application of drill-strings with the considered periodic inserts with sources of local resonance with respect to the well diameter in which it can be used because there is a reduction in clearance.
   2. Does the placement of periodic inserts with sources of local resonance in the drill-string affect the well cleaning and can it cause a stuck pipe?
   3. Can it be used in directional wells?
2. Indicate whether the drill-string with the considered periodic inserts with sources of local resonance was applied in field conditions, where and in which well conditions.
3. The conclusions are too general. Specific data and their numerical values resulting from the research should be added.

Specific comments:

1. Lines 58-60: „The effect of the various design parameters of the periodic inserts with LR on the bandgap characteristics of the drill-string is investigated in an attempt to establish design guidelines of this new class of drill-strings“. Design guidelines of the new class of drill-strings are not explicitly stated in the paper. They need to be added.
2. Table 1. Main physical and geometrical parameters of the drill-string under consideration - Data on drill collars should also be added to the table because they are also part of the drill-string.

Author Response

We appreciate all your constructive comments.

Attached please find our response to ALL your comments.  We have addressed & accommodated all these comments.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper studied the vibration property of the periodic drill-strings with local sources of resonance. The proposed scheme is effective in suppressing the adverse mode in the working condition, as demonstrated by the numerical analysis. The content is of interest for the reader of Vibration Journal. However, some minor modification based on the following comments is required before it can be accepted by the journal for publication.

The local resonance is made of the ViscoElastic material. As we know,  viscoelastic material describes the stress-strain relation dependent on time, where the damping effect is inevitable. How to deal with the damping effect in the dispersion analysis of metamaterial?

Please outline briefly the governing equation of the drill-string in the paper.

The simulation of the drill-strings requires periodic local sources. The drill-string can be viewed as a metamaterial. What not employ Bloch theory and consider only one unit to analyze the dispersion relations?

The modes of vibration in Fig.6 are simulated with a rather coarse mesh, which tends to be inaccurate in capturing the eigenmode compared with finer mesh. We can see in (e), the mesh is severely distorted.

Please comment on the economic effect of the scheme with local resonance.

Author Response

We appreciate all your constructive comments.

Attached please find our response to ALL your comments.  We have addressed & accommodated all these comments.

Author Response File: Author Response.pdf

Reviewer 4 Report

This paper proposes a new class of drill-strings for attenuating undesirable vibrations. Bending, torsional and axial vibrations are considered in the developed model. Simulation results are obtained and compared with conventional pipelines using ANSYS software. The topic is interesting and its writing is good. I raise two points for improvement.

1. Is it accurate enough to model the elements with springs? It could be better confirmed if there are experimental validations.
2. The paper lacks theoretical derivation of the governing motion equations and only ANSYS simulations are carried out.

Author Response

We appreciate all your constructive comments.

Attached please find our response to ALL your comments.  We have addressed & accommodated all these comments.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

thank you for addressing the indications