The definition of a dog leg is a «change in the inclination or direction of the hole». From that point of view, in a directional well, a dog leg is present, starting at the kick-off point. As we start changing the angle of the hole under control, we must add any abrupt dog-leg is a potential changer and the concept of dog-leg severity is useful in grading the dog-leg in order to establish a safe limit.
Dog-Leg severity is defined as a total change in the angle of the hole per 100′. In contrast, A safe dog-leg severity limit relies on the formations drilled, hole’s size, component’s size of the drilling assembly, size of casing to be run so on. The worst complication of a dog-leg is the creation of a Key seat, and in directional drilling, this is a continuous hazard that has to be avoided or eliminated wheneverr it does occur.
Hard or soft interbedded formations.
Frequent corrrections in hole angle or direction.
BHA becomes Jammed in the successive Micro Doglegs
Likely when Picking up for a connection which is possible on trips.
- Angle Change speeding: The main target is to drill a useful well with an inside passable diameter, without dog legs and key seats.