Drillstring Torsional Vibrations: Comparison Between Theory and Experiment on a Full-Scale Research Drilling Rig

Halsey, G. W.; Kyllingstad, Åge; Aarrestad, T.V.; Lysne, D.

doi:10.2118/15564-ms

Cited by 61 publications

(13 citation statements)

References 8 publications

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“…Modifications are made to the pendulum model for individual cases. Halsey et al (1986) derived equations for individual sections of drillstring and developed a computer program to calculate torsional resonance frequencies. Lin and Wang (1991) developed a dry-friction based model and carried out parametric studies to observe the effect of viscous damping, rotational speed and natural frequency on torsional vibration.…”

Section: Torsional Vibrationmentioning

confidence: 99%

Experimental Investigation of the Effects of Rotational Speed and Weight on Bit on Drillstring Vibrations, Torque and Rate of Penetration

Bavadiya

Alsaihati

Ahmed

et al. 2017

Day 3 Wed, November 15, 2017

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Drillstring vibrations namely axial, lateral and torsional vibrations are the primary reason for downhole tool failure and reduction in rate of penetration (ROP). Factors like bit design, bottom hole assembly, bit-rock interaction, rotational speed, wellbore hydraulics, weight on bit (WOB) and drillstring-borehole interaction affect vibrations, out of which only rotational speed and WOB can be changed in real-time to minimize vibrations. It has been a topic of interest to understand and model downhole vibrations, minimize them and find an optimum range of drilling parameters to increase the drilling efficiency. This article presents the results of experimental studies conducted on a fully automated drilling rig to examine the effects of drilling parameters on drillstring vibrations, torque and rate of penetration. The study is different in terms of the high-speed range and the use of axial vibration transmitter to measure the vibration severity as per ISO standards. Experiments were performed on two different rock samples with varying strength. Perfect hole cleaning with negligible fluid flow effect was assumed. Each experiment was run for an average of six minutes collecting an average of 120 data points which were then averaged out for analysis. Parametric study was carried out to analyze the impacts of bit strength to rock strength ratio, bit constant and intrinsic specific energy on torque using existing model. As the drillstring was stiff and small, torsional oscillations were not observed and only lateral and axial vibrations were studied. Effect of drilling parameters and vibration on ROP was studied only on soft rock sample as ROP on hard rock was too small to be recorded Once the input parameters for the analytic model were methodically selected they show good agreement with the experimental data. The results of the parametric study revealed that estimation of torque relies heavily on the bit constant. Axial vibrations increased when rotational speed was near to the natural frequency of the drillstring which resulted in increase of ROP. Type of formation affected the magnitude of lateral and axial vibrations. Reducing both rotational speed and WOB helps to minimize lateral vibrations in hard formations while reducing rotational speed can effectively reduce axial vibrations.

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Section: Torsional Vibrationmentioning

confidence: 99%

Experimental Investigation of the Effects of Rotational Speed and Weight on Bit on Drillstring Vibrations, Torque and Rate of Penetration

Bavadiya

Alsaihati

Ahmed

et al. 2017

Day 3 Wed, November 15, 2017

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“…A consequence of this is that the models are unable to explain the occurrence of stick-slip with the bit off bottom (where there is no bit-rock interaction). Off-bottom stick slip is a well known phenomenon from the field, and when mentioned in literature is hypothesized to be caused by a negative difference between static and dynamic along-string Coulomb-type friction [14][15][16]. This is an important phenomena as it indicates that nonlinear frictional forces along the drill-string (and not just the bit rock interaction), in deviated or horizontal wells, plays a significant role in the torsional oscillatory behavior of drill-strings.…”

Section: Introductionmentioning

confidence: 99%

Stick-slip and Torsional Friction Factors in Inclined Wellbores

Aarsnes

Shor

2018

MATEC Web Conf.

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Abstract. Stick slip is usually considered a phenomenon of bit-rock interaction, but is also often observed in the field with the bit off bottom. In this paper we present a distributed model of a drill string with an alongstring Coulomb stiction to investigate the effect of borehole inclination and borehole friction on the incidence of stick-slip. This model is validated with high frequency surface and downhole data and then used to estimate static and dynamic friction. A derivation of the torsional drill string model is shown and includes the along-string Coulomb stiction of the borehole acting on the string and the 'velocity weakening' between static and dynamic friction. The relative effects of these two frictions is investigated and the resulting drillstring behavior is presented. To isolate the effect of the along-string friction from the bit-rock interaction, field data from rotational start-ups after a connection (with bit off bottom) is considered. This high frequency surface and downhole data is then used to validate the surface and downhole behavior predicted by the model. The model is shown to have a good match with the surface and downhole behavior of two deviated wellbores for depths ranging from 1500 to 3000 meters. In particular, the model replicates the amplitude and period of the oscillations, in both the topside torque and the downhole RPM, as caused by the along-string stick slip. It is further shown that by using the surface behavior of the drill-string during rotational startup, an estimate of the static and dynamic friction factors along the wellbore can be obtained, even during stick-slip oscillations, if axial tension in the drillstring is considered. This presents a possible method to estimate friction factors in the field when off-bottom stick slip is encountered, and points in the direction of avoiding stick slip through the design of an appropriate torsional start-up procedure without the need of an explicit friction test.

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“…Applications are towers under turbulent wind flow [9] and turbomachinery applications [10]. In drilling systems stick/slip of the whole drilling system [11] is a well known consequence of self-excitation.…”

Section: Introductionmentioning

confidence: 99%

“…Several studies have focused on stick/slip of the whole drilling system, the most familiar kind of measured torsional vibration [11,14,15]. In this context, the drilling systems comprises the rig, a drillstring, and a bottomhole assembly (BHA) with measurement tools, and a bit to cut the formation.…”

Section: Introductionmentioning

confidence: 99%

Derivation and experimental validation of an analytical criterion for the identification of self-excited modes in drilling systems

Hohl

Tergeist

Oueslati

et al. 2015

Journal of Sound and Vibration

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Drillstring Torsional Vibrations: Comparison Between Theory and Experiment on a Full-Scale Research Drilling Rig

Cited by 61 publications

References 8 publications

Experimental Investigation of the Effects of Rotational Speed and Weight on Bit on Drillstring Vibrations, Torque and Rate of Penetration

Experimental Investigation of the Effects of Rotational Speed and Weight on Bit on Drillstring Vibrations, Torque and Rate of Penetration

Stick-slip and Torsional Friction Factors in Inclined Wellbores

Derivation and experimental validation of an analytical criterion for the identification of self-excited modes in drilling systems

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