I found this bit interesting:
"Subject: 4. What is Gasoline?
4.1 Where does crude oil come from?.
The generally-accepted origin of crude oil is from plant life up to 3
billion years ago, but predominantly from 100 to 600 million years ago .
"Dead vegetarian dino dinner" is more correct than "dead dinos".
The molecular structure of the hydrocarbons and other compounds present
in fossil fuels can be linked to the leaf waxes and other plant molecules of
marine and terrestrial plants believed to exist during that era. There are
various biogenic marker chemicals ( such as isoprenoids from terpenes,
porphyrins and aromatics from natural pigments, pristane and phytane from
the hydrolysis of chlorophyll, and normal alkanes from waxes ), whose size
and shape can not be explained by known geological processes . The
presence of optical activity and the carbon isotopic ratios also indicate a
biological origin . There is another hypothesis that suggests crude oil
is derived from methane from the earth's interior. The current main
proponent of this abiotic theory is Thomas Gold, however abiotic and
extraterrestrial origins for fossil fuels were also considered at the turn
of the century, and were discarded then. A large amount of additional
evidence for the biological origin of crude oil has accumulated since then.
4.2 When will we run out of crude oil?
It has been estimated that the planet contains over 6.4 x 10^15 tonnes of
organic carbon that is cycled through two major cycles, but only about 18%
of that contributes to petroleum production. The primary cycle ( turnover of
2.7-3.0 x 10^12 tonnes of organic carbon ) has a half-life of days to
decades, whereas the large secondary cycle ( turnover 6.4 x 10^15 tonnes of
organic carbon ) has a half-life of several million years . Much of this
organic carbon is too dilute or inaccessible for current technology to
recover, however the estimates represent centuries to millenia of fossil
fuels, even with continued consumption at current or increased rates .
The concern about "running out of oil" arises from misunderstanding the
significance of a petroleum industry measure called the Reserves/Production
ratio (R/P). This monitors the production and exploration interactions.
The R/P is based on the concept of "proved" reserves of fossil fuels.
Proved reserves are those quantities of fossil fuels that geological and
engineering information indicate with reasonable certainty can be recovered
in the future from known reservoirs under existing economic and operating
conditions. The Reserves/Production ratio is the proved reserves quantity
divided by the production in the last year, and the result will be the
length of time that those remaining proved reserves would last if production
were to continue at the current level . It is important to note the
economic and technology component of the definitions, as the price of oil
increases ( or new technology becomes available ), marginal fields become
"proved reserves". We are unlikely to "run out" of oil, as more fields
become economic. Note that investment in exploration is also linked to the
R/P ratio, and the world crude oil R/P ratio typically moves between
20-40 years, however specific national incentives to discover oil can
extend that range upward.
Concerned people often refer to the " Hubbert curves" that predict fossil
fuel discovery rates would peak and decline rapidly. M. King Hubbert
calculated in 1982 that the ultimate resource base of the lower 48 states of
the USA was 163+-2 billion barrels of oil, and the ultimate production of
natural gas to be 24.6+-0.8 trillion cubic metres, with some additional
qualifiers. As production and proved resources were 147 billion barrels of
oil and 22.5 trillion cubic metres of gas, Hubbert was implying that volumes
yet to be developed could only be 16-49 billion barrels of oil and 2.1-4.5
trillion cubic metres. Technology has confounded those predictions for
natural gas [6a].
The US Geological Survey has also just increased their assessment of US
( not just the lower 48 states ), inferred reserves crude oil by 60 billion
barrels, and doubled the size of gas reserves to 9.1 trillion cubic metres.
When combined with the estimate of undiscovered oil and gas, the totals
reach 110 billion barrels of oil and 30 trillion cubic metres of gas .
When the 1995 USGS estimates of undiscovered and inferred crude oil are
calculated for just the lower 48 states, they totalled ( in 1995 ) 68.9
billion barrels of oil, well above Hubbert's highest estimate made in 1982.
The current price for Brent Crude is approx. $22/bbl. The world R/P ratio
has increased from 27 years (1979) to 43.1 years (1993). The 1995 BP
Statistical Review of World Energy provides the following data [6,7].
Crude Oil Proved Reserves R/P Ratio
Middle East 89.4 billion tonnes 93.4 year
USA 3.8 9.8 years
USA - 1995 USGS data 10.9 33.0 years
Total World 137.3 43.0 years
Coal Proved Reserves R/P Ratio
USA 240.56 billion tonnes 247 years
Total World 1,043.864 235 years
Natural Gas Proved Reserves R/P Ratio
USA 4.6 trillion cubic metres 8.6 years
USA - 1995 USGS data 9.1 17.0 years
Total World 141.0 66.4 years.
One billion = 1 x 10^9. One trillion = 1 x 10^12.
One barrel of Arabian Light crude oil = 0.158987 m3 and 0.136 tonnes.
If the crude oil price exceeds $30/bbl then alternative fuels may become
competitive, and at $50-60/bbl coal-derived liquid fuels are economic, as
are many biomass-derived fuels and other energy sources ."