I believe you mean what are the risks in drilling a hole (oil well) underbalanced. The result can be a blowout and oil well fire. Drillers must keep the right mud weight in order to hold back gas that is trying to come to the surface.

drilling press

Drilling centre and guided drilling get your hole in precisely the correct place.

A sensitive drilling machine is an upright drilling machine. However, a radial drilling machine is also considered a sensitive drilling machine.

Conventional Drilling is the drilling of a vertical well through reservoir rocks to TD. Directional drilling is the drilling of a non-vertical well horizontaly through a source rock.