By slanting or curving wells, it is possible to reach reservoirs under lakes or other environmentally sensitive areas. By turning a full 90 degrees, wells can bore horizontally into formations, greatly increasing productivity by exposing a larger area of the hydrocarbon bearing rock to the well bore.
Drilling at an angle, instead of on the perpendicular, by using a whipstock to bend the pipe until it is going in the desired direction. Directional drilling is used to develop offshore leases, where it is very costly and sometimes impossible to prepare separate sites for every well; to reach oil beneath a building or some other location which cannot be drilled directly; or to control damage or as a last resort when a well has cratered. It is much more expensive than conventional drilling procedures.
The technique of drilling at an angle from the vertical by deflecting the drill bit. Directional wells are often drilled to reach an oil- or gas-bearing reservoir where drilling cannot be done, such as beneath a shipping lane in the ocean. Directional drilling is being used increasingly to intersect reservoirs at angles that exposes more of the rock to the wellbore and increases the amount of oil or gas that flows into the well.