Dogleg Severity (DLS)
Definition - What does Dogleg Severity (DLS) mean?
Dogleg severity is a measure of the change in direction of a well bore over a defined length, normally measured in degrees per 100 feet of length. The more severe a dogleg is, the more potential difficulties arise due to the drill string passing through a curved well trajectory. Problems encountered include the abrasion of the drill string against the curved side and bottom hole assembly becoming stuck.
Trenchlesspedia explains Dogleg Severity (DLS)
A drilling operation is planned with a desired change in angle between two points on the well trajectory. Doglegs most often occur due to changes in rock composition and are unplanned. A severe dogleg, places additional stresses on the drill string due to the tension created by the curve. Damage can be done to the drill string itself and casing cement can be worn away due to the friction of the string rubbing against the cement. There is a risk that the drill string may get stuck when a part jams in the dogleg curve. In very severe cases, the drill may not be able to reach the desired depth due to the dogleg.