8/10/2019 Modelling and Analysis of BHA and Drill-String
Vibrations | School of Engineering | The University of Aberdeen
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27/10/2014 18:42Modelling and Analysis of BHA and Drill-String
Vibrations | School of Engineering | The University of Aberdeen
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Modelling and Analysis of BHA and Drill-String Vibrations
The research project is aimed at developing an
experimentally verified analytical model describing the
vibrations of the Bottom Hole Assembly (BHA) and
drill-string employed in oil and gas extraction. The
project is funded by BG Group. The analytical model
to be developed in the course of the project is hoped
to serve as an aid to the BHA planning process, to
avoid costly field failures.
Our research is focused on developing lower
dimensional models for BHA vibrations with
experimental validation where possible. In our initial
studies, an axial-torsional vibration (2 degree-of-
freedom) model recently proposed in literature was adopted and
modified.
In this model, the coupling between axial and torsional
vibrations arise from the cutting and contact
forces at the bit, and the model involves state-dependent delay
differential equations. A detailed stability
analysis of this model and the development of a Galerkin
projection scheme to tackle the state dependent
delay system, are the key contributions of this study. This
model was subsequently coupled to a lateral
vibration model (considering the near-bit stabilized section).
The combined axial-torsional-lateral model
was solved for varying rotary speeds, weight on bit, and collar
lengths etc. The spring-mass models
studied earlier, though insightful, are of limited practical
use.
With a view to developing realistic reduced order models from
higher dimensional models, an in-house
static Finite Element code for studying BHA in straight,
inclined holes in the presence of borehole
constraint, was developed and validated against commercial FE
code predictions. In an ongoing work, the
utility of Proper Orthogonal Modes (POMs) in reduced order
modelling of BHA is explored. The necessary
higher dimensional data are generated through Finite Element
simulations and will be utilized in the
constructions of the POMs. An in-house experimental rig to
facilitate the study of the BHA and drill-string
dynamics is also currently under construction.
School of Engineering
Fraser Noble Building
King's College
Aberdeen
AB24 3UE
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