déviation

OBS: La déviation s'impose notamment lorsque le forage initial n'a pas atteint l'objectif géologique visé, ou quand un «poisson» qu'il a été impossible de «repêcher» interdit la continuation normale du forage.

OBS: [Sidetracking] can be done with the use of a whipstock, a down-hole tool which forces the drill bit to drill at a slight angle from the vertical. By beginning the deviation of the hole several hundred feet around the junk in the original hole, the new hole will bypass the obstruction and may be taken on down to the pay zone.
OBS: Sidetracking is also done to deepen a well or to relocate the bottom of the well in a more productive zone, which is horizontally removed from the original well.