The
"Horizontal Drilling" term is from the general term
"directional drilling," used where the departure of the well bore from vertical
exceeds about 80 degrees. Note that some horizontal wells are designed such that
after reaching true 90-degree horizontal, the well bore may actually start
drilling upward. In such cases, the angle past 90 degrees is continued, as in 95
degrees, rather than reporting it as deviation from vertical, which would then
be 85 degrees. Because a horizontal well typically penetrates a greater length
of the reservoir, it can offer significant production improvement over a
vertical well.
