Comprehensive review of high frequency torsional oscillations (HFTOs) while drilling

The advancement of downhole sensor technology in the past twenty years has led to the discovery of the phenomenon of high frequency torsional oscillations (HFTOs), which has received increasing attention in the well construction industry in recent years. HFTOs are attributed to self-excited torsional resonance, often encountered while drilling harder rock formations, and are observed to be localized in the lower bottom-hole assembly (BHA) or lower part of the drillstring only. Downhole tangential acceleration and its frequency spectrum are usually used to identify the occurrence of HFTOs, which are believed to be responsible for downhole tool failures such as electronic component failure, cracks on drill collars in the BHA, and loose connections. Various insights into the HFTO mechanism have been gained in the literature through field experiments and observations, data analysis, numerical simulation, and laboratory tests.