Dogleg severity (DLS) measures the rate of change in wellbore direction, typically expressed in degrees per 100 feet (°/100ft) or degrees per 30 meters. DLS quantifies how sharply the wellbore curves, combining changes in both inclination and azimuth into a single metric critical for drilling planning and equipment selection.
Industry Standards and Limits
Conventional drilling operations typically limit DLS to 3-5°/100ft to manage equipment wear and operational risks:
- API RP 7G establishes that casing wear accelerates significantly above 5°/100ft due to drillstring contact forces
- Conventional motors: Limited to approximately 8-10°/100ft maximum build rates
- Advanced RSS systems (SPE-124498-MS): High-DLS RSS can achieve up to 15°/100ft, potentially eliminating motor runs entirely in directional sections
Equipment Impacts
Excessive DLS creates multiple operational challenges: accelerated casing wear at contact points, increased torque and drag during drilling and completions, fatigue stress on drill pipe and BHA components, and difficulties running logging tools and completions equipment.
Modern Capabilities
Recent advances enable aggressive trajectory changes while managing equipment impact:
- HFTO dampers with high-DLS RSS (SPE-223747-MS, 2025): Enabled record-breaking runs by combining high build rates with vibration suppression
Autonomous drilling systems optimize parameters to achieve target trajectories while minimizing the equipment stress associated with high DLS sections.