Investigation on the Effect of High-Frequency Torsional Impacts on the Torsional Vibration of an Oilwell Drill String in Slip Phase

Abstract

The drilling system usually encounters detrimental stick-slip vibration to the drilling process. One of the approaches for controlling the stick-slip vibration is using high-frequency torsional impact (HFTI). However, how the HTFI will affect the vibration of the drill string is still unknown. This study proposed a mechanical model of the drill string by using continuous system to investigate the effect of HFTI on the vibration of a drill string in slip phase, wherein the HFTI is considered in the model. The mechanical model is investigated through using mode superposition method and conducting case studies. Results show that the HFTI is more sensitive to the drill string close to the drill bit and that the HFTI has little effect on the vibration of drill string. During the drilling process, the HFTI aggravates the rock damage and rock failure, which actually improves the drilling efficiency and mitigates the stick-slip vibration.