Understanding the interaction of high-frequency torsional oscillations (HFTO) with other vibrational phenomena is essential to develop effective HFTO mitigation strategies. While coupling with axial vibrations and stick/slip already have been studied extensively, the interaction of HFTO with lateral vibrations has received less attention. The complete paper analyzes this interaction based on a bit/rock interaction model that accounts for the superimposed movement of whirl and HFTO at the bit. The new bit model provides a physics-based explanation of why bit backward whirl and torsional vibrations cannot be observed simultaneously.
Introduction
The torsional movement of HFTO is localized to the lower part of the bottomhole assembly (BHA). The amplitudes along the distance from the bit are scaled by complex mode shapes with a comparably small wavelength.
