norwest cheers arrowsmith-2 flows ..., page-72

Hi Shadders for your information

By Walter K. Merschat
Exploration Geologist, Unocal, 1969-76; Geoscientist, Gulf Research, 1976-84;
Consultant, Scientific Geochemical Services, 1985-present


WHAT IS DIRECTIONAL DRILLING?
Directional drilling is an advanced technology
that allows oil and gas resources to be
tapped a long horizontal distance away from the
well site. For the purposes of this report,
“directional drilling” will encompass all forms of
drilling where the endpoint of the well is distant
from the drill site, rather than directly beneath it.
Under this definition, slant-hole wells, S-turn
wells, and horizontal wells are all considered
forms of directional drilling. The term
“directional drilling” can also be used to describe
drilling to lay subsurface pipelines beneath rivers
and other sensitive areas; this application of
A brief synopsis of directional well types
follows, of the various directional well types.
Slant-Hole Wells
Slant-hole wells are drilled at an angle from
the vertical, using a tilting drilling rig. Slant-hole
wells can be completed without making any
bends at all, resulting in the equivalent of a
conventional vertical well that is tilted on its
axis. Alternately, slant-hole wells can be
combined with a horizontal bend that is drilled in
much the same way as traditional horizontal
wells

Sometimes known as “deviated wells,” Sturn
wells start out in a near-vertical orientation,
have a long near-horizontal or diagonal section,
and finish by approaching the vertical once
again. This well type has been used in extendedreach
applications. For example, the Sacate Sa-1,
an offshore California well, achieved a
horizontal distance of over 3½ miles from the
well site using this drilling technique (Elks and
Masonheimer 2002).
Horizontal Wells
Horizontal wells are defined as wells
deviated more than 75 degrees from vertical
(Lacy et al. 1992); they often depart from the
horizontal in order to track the dip of the target
formation. These wells have a characteristic “J”
shape, with the horizontal section following the
oil- or gas-bearing rock to maximize production.
Short-Radius
Short-radius wells feature a sharp, abrupt turn
from the vertical to the horizontal plane. A
comprehensive review of short-radius horizontal
drilling found that “[r]eservoir management
applications, water and gas coning, injection
wells, irregular formations and coal degasification
[coalbed methane production] are
becoming more economically feasible” (Leazer
and Marquez 1995). This study found that short
radius horizontal wells make it easier to avoid
problem formations above the pay zone. And
with short-radius wells, submersible pumps can
be placed deeper in the wellbore, improving
pumping efficiency and extending pump life.
The study concluded that “[s]hort radius technology
has evolved to the point where it is a
common occurrence to drill a 45-ft radius curve
into a 10-ft target and achieve displacements in
excess of 1,000 ft.” These wells are not typically
used to drill long horizontal distances from the
well site.
Medium Radius
Medium-radius wells make their turn from
the vertical to the horizontal at an intermediate
rate, and the horizontal length is often longer.
By the early 1990s in the United States, mediumradius
wells were the most widely used and
productive of horizontal wells (USDOE 1993).
In 1990, the longest horizontal displacement for
a medium-radius horizontal well reached 4,164
feet (Moritis 1990). This drilling style figures
Figure 1. Different types of directional wells.
Slant-Hole
Slant-
Hole
S-Turn
Short-Radius
Medium-Radius
Long-
Radius
Stacked
Laterals
Opposing Laterals
Sidetracking from
Vertical Well
Horizontal Wells
Single Wells Multilateral Wells
Horizontal from

So yes it all stacks up to a Horizontal flow
DYOR
Go NWE you good thing
Cheers Janus