Dynamic Modeling of Directional Drillstring: A Linearized Model Considering Well Profile

Abstract

Drillstring vibration can cause fatigue failure of the drill pipe, premature wear of the bit, and a decreased drilling efficiency; therefore, it is important to accurately model the drillstring and bottomhole assembly (BHA) dynamics for vibration suppression. The dynamic analysis of directional drilling is more important, considering its wide application and the advantage of increasing drilling and production efficiencies; however, the problem is complex because the large bending can bring nonlinearities to drillstring vibration and the interaction with the wellbore can occur along the entire drillstring. To help manage this problem, this paper discusses a dynamic finite element method (FEM) model to characterize directional drilling dynamics by linearizing the problem along the well's central axis. Additionally, the rig force and drillstring/wellbore interaction are modeled as a boundary condition to simulate realistic drilling scenarios. The proposed modeling framework is verified using comparisons with analytical solutions and literatures. The utility of the proposed model is demonstrated by analyzing the dynamics of a typical directional drillstring.