Session: 11-01-01 Well Drilling Technology

Paper Number: 125722

125722 - Analytical and Numerical Study on Torsional Vibration of Drill String Under Weight on Bit Fluctuation 

In deepwater offshore drilling, a drill pipe is suspended from the drillship, and load and rotation are applied to the drill bit through the drill pipe to drill the formation. Therefore, to properly control the behavior of the drill bit, it is crucial to understand the dynamics of the entire drill string. In particular, torsional vibration is important to consider for drilling efficiency because it affects the rotational speed of the drill bit. In previous studies, torsional vibration has been studied mainly in terms of self-excited vibration excited by stick-slip caused by friction between the drill bit and the drilling formation. In such studies, the weight on bit is considered constant or only slightly fluctuates due to self-excited oscillations caused by bit bounce. However, due to ship heaving, the WOB is subject to large forced oscillations in deepwater offshore drilling. Our previous study showed that such WOB fluctuations had a non-negligible effect on the torsional vibration. Therefore, it is important to consider the influence of such heave-induced weight on bit fluctuations in torsional vibration in deepwater offshore drilling.

In this study, analytical and numerical studies are conducted to investigate the torsional vibration of a drill string when the weight on bit fluctuates. First, through the analytical solution of a single-mass model, we clarify how the regular vibration of the weight on bit affects the torsional vibration of the drill string. Next, numerical experiments are conducted on the torsional vibration by modeling an actual drill string using a multi-mass model, given irregular fluctuations in the weight on bit due to heave.

As a result, we clarified the relationship between the amplitude and period of weight on bit fluctuation, the amplitude of torsional vibration, and the occurrence of stick-slip. In addition, we discussed the actual phenomena that could occur.

Finally, we discussed the critical factors for suppressing torsional vibration in ultra-deepwater drilling through these considerations.

Presenting Author: Tatsuya Kaneko Japan Agency for Marine-Earth Science and Technology

Presenting Author Biography: Tatsuya Kaneko is a postdoctoral researcher at Japan Agency for Marine-Earth Science and Technology. His research interests are in drill string dynamics and hybrid modeling.

Authors:

Tatsuya Kaneko Japan Agency for Marine-Earth Science and Technology
Tomoya Inoue Japan Agency for Marine-Earth Science and Technology
Ryota Wada The University of Tokyo
Tokihiro Katsui Kobe University
Hiroyoshi Suzuki Osaka University