Environmental Engineering Reference
In-Depth Information
off New Orleans and since 1999 producing 1.25 PJ of oil
and gas per day (SEPCo 2006), repaid the energy cost of
its construction in less than a week of crude oil and natu-
ral gas extraction.
The net energy ratio of crude oil extraction can surpass
0.97 or even 0.995 (EROI 33-200) in rich fields, but
averages in old hydrocarbon provinces are lower. Cleve-
land (2005) estimated that EROI for U.S. oil discovery
and extraction in 1930 averaged at least 100 and calcu-
lated that average EROI of the country's hydrocarbon
production (measured in thermal equivalents) rose from
17 to 25 between 1954 and 1970, declined to about 12
by 1983, rose to 20 by 1992, and then declined slightly
afterwards (fig. 10.1). A similar pattern, but much lower
rates of return (just above 10 during the 1990s), results
when taking into account the energy quality of produc-
tion inputs (electricity, refined fuels) and outputs (crude
oil, unprocessed gas). My calculations based on Syncrude
Canada (2006) data indicate that mining of Alberta oil
sands, extraction of bitumen, and its upgrading to light
sweet crude oil has EROI around 6. Steam-assisted
gravity drainage is the dominant method of oil sand ex-
traction. It needs about 1 J of natural gas for steam gen-
eration for every 5 J of heavy bitumen, and the overall
EROI of this recovery, including the cost of extraction
and delivery of the gas, the cost of upgrading, and an av-
erage 15% bitumen loss, is no higher than 3.
Energy investment in oil transportation is relatively
small compared to the energies that these systems deliver
over their lifetimes. Energy embodied in steel, the domi-
nant material in pipeline construction, amounts to less
than 3.5 TJ/km for a 60-cm diameter pipeline, and con-
struction adds about 1.5 TJ/km, for a total cost of about
5 TJ/km, or to less than 0.1% of energy in the oil that
the pipeline will carry during its 30-40 years of service.
High-capacity pipelines need on the order of 200 kJ/t-
km to operate, and the size-dependent requirements for
crude oil tankers range from 150 kJ (for ships
<
50,000
dwt) to less than 50 kJ/t-km for supertankers. Moving
crude oil 1300 km through the TransAlaska pipeline
thus costs only 0.5% of energy in the pumped crude
(Alyeska 2003), and shipping it 3800 km by tankers
from Valdez to Long Beach, California, doubles the cost
to 1% of the energy contained in the oil. Similarly, a
300,000-dwt supertanker moving Saudi oil to the United
States needs an equivalent of about 1% of the fuel it car-
ries in order to travel more than 15,000 km. Energies
needed for the construction of gathering pipelines, oil
terminals, and tankers prorate to 1-3.5 GJ/t.
Oil refining is the most energy-intensive segment of
the entire sequence of liquid fuel production because
even the simplest thermal distillation claims on the order
of 4% of energy content in the processed crude oil. U.S.
10.1
Thermal equivalent EROI for U.S. hydrocarbon produc-
tion, 1954-1997. From Cleveland (2005).
