Effect of shock subs on self-excited vibrations in drilling systems

Ulf Jakob F. Aarsnes (Corresponding author), Nathan van de Wouw

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Uittreksel

The present paper studies the effect of an axial elastic tool (known as a shock sub), mounted downhole in the drill-string, on the occurrence of axial and torsional self-excited vibrations. In particular, we evaluate the feasibility of stabilizing the axial dynamics, dominated by a bilateral (feedback) coupling between the bit-rock interaction and the drill-string wave-equations, through the insertion of a passive down-hole tool. We consider the problem of unwanted drill-string vibrations and explain how these vibrations relate to the so-called axial instability using a distributed parameter (infinite dimensional) model. The equations describing the feedback system causing this instability are derived and then extended to accommodate for the inclusion of the effect of the shock sub. Conditions for the design parameters of the shock sub needed to avoid axial instability are then derived and their practical feasibility are considered.

Originele taal-2Engels
Artikelnummer106217
Aantal pagina's14
TijdschriftJournal of Petroleum Science and Engineering
Volume181
DOI's
StatusGepubliceerd - 1 okt 2019

Vingerafdruk

Drill strings
Vibrations (mechanical)
vibration
Drilling
drilling
Feedback
wave equation
Wave equations
Rocks
rock
effect
parameter

Citeer dit

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abstract = "The present paper studies the effect of an axial elastic tool (known as a shock sub), mounted downhole in the drill-string, on the occurrence of axial and torsional self-excited vibrations. In particular, we evaluate the feasibility of stabilizing the axial dynamics, dominated by a bilateral (feedback) coupling between the bit-rock interaction and the drill-string wave-equations, through the insertion of a passive down-hole tool. We consider the problem of unwanted drill-string vibrations and explain how these vibrations relate to the so-called axial instability using a distributed parameter (infinite dimensional) model. The equations describing the feedback system causing this instability are derived and then extended to accommodate for the inclusion of the effect of the shock sub. Conditions for the design parameters of the shock sub needed to avoid axial instability are then derived and their practical feasibility are considered.",
keywords = "Distributed parameter systems, Drill-string vibrations, Hyperbolic systems, Infinite dimensional systems, Stability, Stick-slip",
author = "Aarsnes, {Ulf Jakob F.} and {van de Wouw}, Nathan",
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Effect of shock subs on self-excited vibrations in drilling systems. / Aarsnes, Ulf Jakob F. (Corresponding author); van de Wouw, Nathan.

In: Journal of Petroleum Science and Engineering, Vol. 181, 106217, 01.10.2019.

Onderzoeksoutput: Bijdrage aan tijdschriftTijdschriftartikelAcademicpeer review

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