Conventional wells are drilled vertically from the surface straight down to the pay zone. This is the traditional and still common type of 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.
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.
Drilling has advanced from slant and horizontal drilling to drilling that can change direction and depth several times in one well bore. A schematic of these drill bores (often several from the same drill pad, resembles the roots of a plant. This type of drilling is uniquely suited to pay zones in the Lloydminster area which are often distributed like prairie sloughs across the underground landscape. Directional drilling is also being applied in other parts of the world now such as Venezuela and where there is a special need to limit environmental impact on the surface.
(left to right) Conventional, Slant, Horizontal