Understanding How the Placement of an Asymmetric Vibration Damping Tool Within Drilling While Underreaming Assemblies Can Influence Performance and Reliability

摘要

This paper describes the work, on test rigs and full-scale drilling rigs, carried out with respect to placement of an Asymmetric Vibration Damping Tool (AVDT) within drilling while underreaming operations. An AVDT, by virtue of the forward synchronous motion imposed on the drill string, offers benefits in minimizing down hole vibration related tool failures and therefore maximizing ROP. Of interest in using the AVDT is the tendency to minimize stick slip by means of the parasitic torque it generates. This is of particular importance during underreaming operations. While underreaming, stick slip can result in low ROP and potentially an increased incidence of down hole tool failures. The use of an AVDT in these operations has been shown to significantly reduce stick slip. However, due to the forward synchronous motion caused by the AVDT, there is the potential to cause eccentric wear to BHA components in the vicinity of the AVDT. If allowed to progress, this eccentric wear can cause a reduction in down hole tool life and drilling performance. Eliminating eccentric wear would be beneficial in reducing repair costs, extending component life and further improving drilling performance. To minimize eccentric wear and maximize drilling performance, the placement of the AVDT within the bottom hole assembly is critical. This paper describes how the placement of intermediate stabilizers between the AVDT and the underreamer can minimize eccentric wear to the underreamer and the adjacent drill string due to the forward synchronous whirl induced by the AVDT. This approach allows the full benefits of the AVDT to be recognized while reducing the potentially damaging effects of eccentric wear to other BHA components. The work has drawn upon small scale rig testing, full scale testing at the Ullrigg test facility in Norway and from real-world drilling and underreaming operations in the USA.