Analytical, Numerical, and Field Data Investigation for Deriving the Condition of Stick-Slip Drill String Vibration

Abstract

Abstract Several studies have been conducted on the stick-slip type of torsional vibration, which reduces drilling efficiency and sometimes damages drill bits and pipes, using numerical experiments, small-scale model experiments, or field data on the land rig. However, an analytical investigation into stick-slip conditions or a field data investigation of deepwater drilling has not been sufficiently studied. This study derives the conditions for stick-slip occurrence through analytical, numerical, and field data investigations and discusses a method to reduce stick-slip vibration. First, we derive a simple expression for stick-slip using an analytical solution of a single mass-spring-damper model. Additionally, we numerically experiment using a multi-mass model to consider the mass distribution that cannot be considered in the analytical solution. Furthermore, we analyze the field data from deepwater drilling and experiment with a numerical model to examine the actual phenomena. As a result, the analytical and numerical investigations have shown that stick-slip can be prevented by appropriately adjusting the rotational speed and the weight on bit. However, the field data investigation showed that the forced torsional vibration due to the vibration of the weight on bit was predominant in deepwater drilling. In this case, suppressing the amount of fluctuation of weight on bit is crucial to reduce the torsional vibration.