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.

  • Causes:

Hard or soft interbedded formations.

Frequent corrrections in hole angle or direction.

BHA becomes Jammed in the successive Micro  Doglegs

  • Indications:

Likely when Picking up for a connection which is possible on trips.

Circulation unrestricted.

  • Angle Change speeding:  The main target is to drill a useful well with an inside passable diameter, without dog legs and key seats.


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