Abstract
Inducing vibrations while drilling is a relatively new concept that shows promise in directional applications. Instigating motion of the drill string, particularly in the sections lying on the low-side of the wellbore, can lead to substantial improvements in managing the two limiting factors of the long horizontal wells that are typically associated with today's unconventional shale plays: removal of formation cuttings from the borehole, and frictional drag between non-rotating drill strings and the wellbore wall. Minimizing these effects, by introducing controlled vibrations, increases the overall drilling efficiency and reduces the cost associated with the well. The difficulty in implementing such actions, however, is consistency. Because the behavior of drilling assemblies is inherently nonlinear, it has been difficult in the past to reliably predict their response to dynamic events. This, in turn, creates a challenge when trying to optimize the performance of arbitrary Vibration Inducing Devices (VIDs).
This paper presents a detailed analysis of the fully coupled, three-dimensional, nonlinear behavior of drill strings under the action of induced vibrations. Specific focus is given to the dynamic characteristics of a drill string, during horizontal drilling operations, in long unconventional wells and how this behavior affects the success of the well. The response of the drill string, due to induced axial and lateral oscillatory motions, is examined through linearized dynamic analysis and nonlinear timedomain simulations.
Solutions obtained from the study provide a clearer understanding of the dynamics experienced down-hole and lead to suggestions for improved practices when drilling with lateral VIDs, particularly with regards to hole-cleaning. Further insights into the sliding and rotational behavior of the drill string, while using these types of tools, are drawn from animated modeling results. Finally, the future applications of this technology are discussed.
