Stability analysis of drillstring rotation

Palmov, Vladimir; Brommundt, Eberhard; Belyaev, Аlexander K.

doi:10.1080/02681119508806197

Cited by 22 publications

(9 citation statements)

References 7 publications

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“…The equation is independent of the length L of the torsional oscillator. This is in accordance with the literature if the characteristic of the excitation does not change with the length [17]. This is true for the examined case because the mode shapes are localized to a small portion of the drilling system.…”

Section: Analytical Examplesupporting

confidence: 87%

“…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. Stick/slip in drilling dynamics is denoted as self-excitation of the first torsional mode of the whole drilling system caused by a falling torque characteristic of cutting forces and friction forces at the bit from a global point of view [16,17]. In several studies the root cause of stick/slip is attributed to mode coupling between axial and torsional vibrations [18][19][20] or to regenerative effects [21].…”

Section: Introductionmentioning

confidence: 98%

“…In several studies the root cause of stick/slip is attributed to mode coupling between axial and torsional vibrations [18][19][20] or to regenerative effects [21]. Lumped mass models [22], analytical models [17], and models based on finite elements [23][24][25][26][27] have been used to analyze stick/slip in drilling systems. Based on these models, stability considerations have been made to identify safe drilling parameters that prevent stick/slip [17,28].…”

Section: Introductionmentioning

confidence: 99%

“…Lumped mass models [22], analytical models [17], and models based on finite elements [23][24][25][26][27] have been used to analyze stick/slip in drilling systems. Based on these models, stability considerations have been made to identify safe drilling parameters that prevent stick/slip [17,28].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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Section: Analytical Examplesupporting

confidence: 87%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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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“…Their understanding is thus fundamental to the improvement of the drilling process. 0 The stick-slip vibrations experienced by rotary drilling systems are conventionally analyzed by modeling the drillstring as a torsional pendulum and the bit/rock interaction as a reactive torque that decreases with the bit angular velocity, in apparent accordance with measurements from field experiments [4][5][6][7][8][9][10]. However, an alternative approach to predict stick-slip oscillations of the bit was proposed by Richard et al [1,2].…”

Section: Introductionmentioning

confidence: 99%

Instability regimes and self-excited vibrations in deep drilling systems

Depouhon

Detournay

2014

Journal of Sound and Vibration

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This paper analyzes the stability of the discrete model proposed by Richard et al. [1,2] to study the self-excited axial and torsional vibrations of deep drilling systems. This model, which relies on a rate-independent bit/rock interaction law, reduces to a coupled system of state-dependent delay differential equations governing the axial and angular perturbations to the stationary motion of the bit. A linear stability analysis indicates that, although the steady-state motion of the bit is always unstable, the nature of the instability depends on the nominal angular velocity Ω 0 of the drillstring imposed at the rig. On the one hand, if Ω 0 is larger than a critical velocity Ω c , the angular dynamics is responsible for the instability. However, on the timescale of the resonance period of the drillstring viewed as a torsional pendulum, the system behaves like a marginally stable one, provided that exogenous perturbations are of limited magnitude. The instability then only appears on a much larger timescale, in the form of slowly growing oscillations that ultimately lead to an undesired drilling regime such as bit-bouncing or stick-slip vibrations. On the other hand, if Ω 0 is smaller than Ω c , the instability manifests itself on the timescale of the bit motion due to a dominating unstable axial dynamics; perturbations to the steady-state motion then rapidly degenerate into stick-slip limit cycles or bit-bouncing. For typical deep drilling field conditions, the critical angular velocity Ω c is virtually independent of the axial force acting on the bit and of the bit bluntness. It can be approximated by a power law monomial, a function of known parameters of the drilling system and of the intrinsic specific energy (a quantity characterizing the energy required to drill a particular rock). This approximation holds on account that the dissipation in the drilling structure is negligible with respect to that taking place through the bit/rock interaction, as is typically the case. These findings are further illustrated on an example of deep drilling and shown to match the trends observed in the field.

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