Environmental Engineering Reference
In-Depth Information
1980 are above 2.2 Tbbl, or 300 Gtoe, with the mid-
point of recent assessments at about 3 Tbbl, or just over
400 Gtoe.
But because almost two-thirds of the world's oil
reserves are in more than 300 giant fields, whose discov-
eries peaked in the early 1960s, Campbell and Laherr
`
re
(1998) saw no possibility of large-scale additions to the
known oil pool and concluded that some 92% of all oil
we will eventually recover has already been discovered.
They also questioned the common expectation that addi-
tions to reserves in existing oil fields can appreciably delay
the onset of declining output. In contrast, Odell (1984)
thought 2 Tbbl of undiscovered oil to be an ultrapessi-
mistic estimate, concluded that ''the world is running
into oil, not out of it'' (Odell 1992, 285), and put the
total oil in place at 3 Tbbl (Odell 1999). The USGS
world assessment (Ahlbrandt et al. 2006) concluded that
the mean value of the grand total of undiscovered con-
ventional oil, reserve growth in discovered fields, and
cumulative production up to the year 2000 was 3.021
Tbbl, 72% above the Campbell and Laherr`re value.
Laherr`re (2001) dismissed the precursor of this as-
sessment, but he previously conceded that adding me-
dian estimates of undiscovered natural gas liquids (200
Gbbl) and nonconventional oil (700 Gbbl) would yield
up to 1.9 Tbbl of oil yet to be produced (Laherr
`
re
1996). Long-term prospects for the duration of an oil
era must also consider the reserves in nonconventional
deposits, which include very heavy crude oils, oil shales,
and tar sands. Heavy crudes require special methods of
recovery, and shales and sands have typically only small
shares of oil (
<
10%) in the parental rock. The Athabasca
oil sands in northern Alberta contain about 2.5 Tbbl of
bitumen in place, of which some 315 Gbbl are poten-
tially recoverable. In 2004, Canada's conventional crude
oil and condensate reserves were about 5.2 Gbbl, but the
Canadian Association of Petroleum Producers lists 6.9
Gbbl in oil sands under production, and the Alberta En-
ergy and Utilities Board puts the remaining oil sands
reserve under active development at 174.4 Gbbl of bitu-
men (CAPP 2005). When the Oil & Gas Journal added
the latter total to its summary of crude oil reserves
(Radler 2002), it boosted the global aggregate by about
17% and also diminished OPEC's share by more than
10%.
Long-term global assessments of natural gas supplies
must also consider the existence of nonconventional
resources. Conventional natural gas reserves added up to
about 180 Tm
3
by the end of 2000, an equivalent of
about 1.1 Tbbl (or roughly 150 Gt) of crude oil. They
more than doubled between 1980 and 2005, and this
substantial recent increase means that despite the nearly
doubled extraction since 1980, the global R/P ratio in
2005 was about 67 years, compared to 56 years in 1980
and to just over 40 years in the early 1970s (BP 2005).
Conventional reserves are concentrated in Russia (@27%
of the total), Iran (@15%), Qatar (@14%), and Saudi Ara-
bia and the United Arab Emirates (4% each). The Middle
East claims about 40% of all reserves, much less than its
share of crude oil. National R/P ratios range from less
than 10 years for the United States to just over 80 years
for Russia and more than a century for every major Mid-
dle Eastern natural gas producer.
As for the fuel's future, there are two opposing schools
of thought. Pessimists argue that the ultimate resources
of natural gas are actually smaller than those of crude
oil, whereas those who believe in a gas-rich future say
that the Earth's crust holds much more gas, albeit at
depth and in formations currently categorized as non-
conventional resources. Laherr`re (2000) estimates ulti-
