What are the seven purpose of directinal drilling?

Answer 1

Directional wells are drilled for a number of purposes:

Increasing the exposed section length through the reservoir by drilling through the reservoir at an angle
Drilling into the reservoir where vertical access is difficult or not possible. For instance an oilfield under a town, under a lake, or underneath a very difficult to drill formation
Making it cheaper to drill, by having more wellheads together. For instance on an oil platform or jacket offshore, where up to about 40 wells can be grouped together. The wells will fan out from the platform into the reservoir deep below.
Drilling "relief wells" to relieve the pressure of a well which is producing without restraint (blown out).

With modern technology great feats can be achieved. Whereas 20 years ago wells drilled at 60 degrees through the reservoir were achieved, horizontal drilling is now quite normal. However, drilling out far from the surface location is still something that requires careful planning and design: the current record holders manage wells of over 10,000m (32,000 ft) away from the surface location at a depth of only 1,600-2,600m (5,200-8,500 ft). These are all wells drilled from a land location to underneath the sea (Wytch Farm (BP), south coast of England, ARA (Total), south coast of Argentina (TFE) Dieksand (RWE), north coast of Germany, and most recently Chayvo (ExxonMobil), east coast of Sakhalin Island, Russia.

SORRY I KNOW ONLY THIS MUCH