Stick-slip is a destructive drilling dysfunction where the drill bit alternately stops rotating (sticks) and suddenly accelerates (slips), causing severe torsional vibrations throughout the drill string. This oscillation occurs at frequencies of 0.1-2 Hz, with bit speed varying from zero to 2-3 times the applied surface rotary speed.
Vibration Mechanics
During the stick phase, the bit stops while the drill string continues winding up like a torsional spring. When friction is overcome, stored energy releases suddenly, accelerating the bit to 2× or more of surface RPM. This creates extreme torque fluctuations and impact loading on all BHA components.
Industry Impact
Research documents severe economic consequences:
- ROP reduction: 30-50% compared to smooth drilling
- Tool failures: 20-30% of all downhole tool failures attributed to adverse drilling dynamics (SPE 127413)
- Annual cost: Approximately $750 million industry-wide for vibration-related repairs and failures
Mitigation Approaches
- Adaptive PDC bits (SPE/IADC 184736, 2017): 35% torque reduction, 90% variation reduction through mechanically adaptive cutter elements
- Near-bit torsional dampers (SPE-223747-MS, 2025): 99-100% HFTO reduction versus offset runs
- Downhole automation: Real-time thrust modulation at the bit prevents stick-slip onset
NexTitan eliminates stick-slip through autonomous downhole control, maintaining smooth rotation regardless of formation conditions.