Geoscience Reference
In-Depth Information
and physical geography. The ongoing search for unconven-
tional oil supplies depends on an understanding of sedi-
ment, rock strata, and mapping to isolate the various plays
that contain mineable petroleum. Dealing with the potential
environmental issues requires an understanding of streams,
the carbon cycle, and groundwater. You will likely hear about
these issues at various times in your life, and perhaps you
may think about them if the price of gas rises dramatically
at some point in the future. Your understanding of physical
geography will enable you to better understand the choices
that need to be made.
KEY CONCEPTS TO REMEMBER ABOUT
UNCONVENTIONAL OIL SUPPLIES IN
NORTH AMERICA
1.
The United States was the world's leading oil producer
from 1900 until 1970.
2.
U.S. oil production peaked in the early 1970s. In the
face of a greater demand, we began to import increas-
ing amounts of oil. Much of this imported supply came
from politically unstable OPEC nations, raising ques-
tions about national security.
A combination of fluids—
chemicals, oil, and natural
gas—flows from the well.
3.
Oil prices have varied dra-
matically in the past 40 years
due to fluctuations in supply,
political instability, population
growth, economic conditions,
and demand.
Pressurized fluid of
chemicals, sand, and
water is injected into
the well.
Dozens of tanker
trucks deliver water
for the fracking process.
Oil and natural gas
flow to market.
This combination of fluids,-
must be stored on
-
site
—
typically in pits
—
before
treatment, recycling, or
d
isposal.
4.
With conventional oil supplies
waning, recent efforts have fo-
cused on developing unconven-
tional resources. The largest of
these sources in North America
are found in the Canadian oil
sands and various shale plays in
the United States.
Near-surface
groundwater
Casing
Saturated sandstone
Natural gas flows from fissures
into well
5.
Extraction of unconventional oil
is conducted by nontraditional
methods such as open-pit min-
ing and fracking. These meth-
ods may have serious environ-
mental impacts.
The pressurized fluid
creates fissures, or
cracks, in the shale
Target shale
(a)
Figure 20.29 Hydraulic fracturing
(a)
Schematic illustration of the fracking
process. Fracking is the method used to
extract oil and natural gas from shale de-
posits buried deep within the ground.
The wellbore passes through a series of
geological strata to reach the host shale.
At that point the drill turns horizontally to
access as much shale as possible. Water,
sand, and various chemicals are then in-
jected into the shale so that it fractures,
releasing the trapped oil and natural gas.
Note the infrastructure at ground level re-
quired to work the well. (b) Satellite view
of western North Dakota and eastern Mon-
tana at night. The cluster of lights within
the circle results from equipment, build-
ings, and gas flares associated with work
in the Bakken shale play.
Manitoba
Saskatchewan
Minot
Williston
North Dakota
Montana
Bismarck
Dickinson
(b)
