Types of Drilling
Conventional Drilling
Conventional wells are drilled vertically from the surface straight down
to the pay zone. This is the traditional and still common type of drilling.
Horizontal Drilling
Using technologies such as bottom driven bits, drillers are able to
execute a sharp turn and drill horizontally along a thin pay zone. In a related
procedure, developed in this area, two horizontal well bores are drilled one above the
other, about 3 meters apart. One application for this is SAGD (Steam Assisted
Gravity Drainage) where steam is injected into the higher of these horizontal holes and
the heat precipitates oil down into the lower hole, increasing production of heavy
oil. Drilling these holes requires an experienced crew, precision techniques and
advanced technology.
Slant Drilling
Drilling at an angle from perpendicular (commonly 30° to 45°).
This approach minimizes surface environmental disturbance. For example, oil reserves
under a lake can be tapped by a slant hole drilled from on shore. More commonly in
this area; four, six, even eight slant wells are drilled from one "pad" (i.e.
well lease site). This allows the oil reserves under a large land area to be tapped
by only one well site. Thus, production of valuable oil reserves is effectively
harmonized with conserving the environment.
