Definition
Dogleg Severity — Dogleg severity (DLS) is the rate of change of a wellbore's direction, expressed in degrees per 100 feet (or 30 meters), combining changes in both inclination and azimuth to quantify how sharply the hole is curving.
Also known as: dogleg severity, DLS, dogleg
What dogleg severity measures
Dogleg severity quantifies how fast a wellbore is bending. It is calculated from consecutive directional surveys and reported as degrees per 100 ft or per 30 m, accounting for changes in both inclination and azimuth. A build section may run several degrees per 100 ft, while a tangent section aims for near-zero DLS. Directional drillers plan a target DLS and use MWD to confirm the achieved curvature as they steer.
Why it matters mechanically
High or abrupt doglegs raise bending stress in the drill string every time a joint rotates through the curve, accelerating drill pipe fatigue and connection failures. Severe doglegs also create key seats, increase torque and drag, and can prevent casing or tools from passing. A smooth, controlled DLS from a rotary steerable system protects the string and makes the well easier to complete.
Why it matters for rentals
Wells with aggressive doglegs demand fatigue-inspected pipe and correctly designed BHAs to survive cyclic bending.
Rent inspected drill pipe rated for your dogleg profile, or contact us for help selecting a string and BHA for high-DLS trajectories.