A seminar by Roman Shor, a PhD candidate in Petroleum Engineering at the University of Texas at Austin and visiting student at the University of Cambridge, Dynamics and Vibrations Group, Department of Engineering, was held on Friday 20th November 2015.
The response of the drilling system to axial and torsional vibration inputs has a significant impact on drilling performance. Usually the goal is to minimize dynamic response to limit the effects of potentially damaging phenomena in the low frequency range (e.g. bit bounce and torsional stick-slip) and high frequency range (e.g. axial chatter and torsional resonance). However, in some cases the goal is to maximize dynamic response, for example when introducing oscillation tools to overcome wellbore friction while directional drilling or to free stuck pipe. Whether the intention is to maximize or minimize, a suitable mathematical model is required. A transfer matrix model is proposed to predict the harmonic response of the drillstring and is then compared with various field studies, including bit bounce and induced axial oscillation.