Influence of torsional stick-slip vibration on whirl behavior in drill string system

Abstract

Torsional and lateral vibrations, which are important causes of drill string failure, are harmful vibration modes that can occur during drilling. As its form of expression, stick-slip and whirl significantly limit the drilling efficiency and the bottom hole assembly (BHA) performance. Prediction of the correlation between these vibration modes has an important significance in adjusting basic parameters to avoid the effects of stick-slip and whirl vibration in the drilling process. In this work, in order to provide a general understanding of the vibration mechanism, a coupled torsional stick-slip and whirl model with 6 degrees of freedom (6-DOF) was proposed, and numerical simulations were conducted. The Lagrange method was used to derive the model, and the stabilizer-borehole wall interaction, drill collar-borehole wall interaction, and bit-rock interaction were additionally considered. Torsional vibrations were modeled with respect to the entire drill string system, while the lateral vibration was restricted to the BHA part. The results showed a correlation between torsional and lateral vibration modes when stick-slip vibration occurs and disappears. These correlations were performed by analyzing the time domain, frequency domain, and correlation coefficients. The relationship between torsional and lateral vibration modes was verified by performing a qualitative comparison with field experiments.