Page 17 - Synthetic Fuels Handbook

FUEL SOURCES 5

and potential for coke formation in thermal process, to mention only three of the affected
properties. In addition to the organic constituents, there are also metal-containing constitu-
ents (notably those compounds that contain vanadium and nickel) which usually occur in
the more viscous crude oil in amounts up to several hundred parts per million.
Physical methods of fractionation of petroleum and heavy oil can be achieved to produce
four bulk generic fractions: saturates, aromatics, resins, and asphaltenes (Speight, 2001).
Relative amounts of these fractions have often been equated to the behavior of petroleum
or heavy-oil feedstocks during recovery and refining (Speight, 2007).

1.2 NONCONVENTIONAL FUEL SOURCES

Nonconventional fuel sources are sources of fuels (alternate or synthetic fuels) other than
traditional petroleum (Tables 1.2–1.3) (Cooke, 2005).
Gaseous, liquid, or solid synthetic fuels are obtained by converting a carbonaceous material
to another form. The most abundant naturally occurring materials suitable for this purpose
are (a) tar sand, (b) coal, and (c) oil shale. The conversion of these raw materials to synthetic
fuels can replace depleted, unavailable, or costly supplies of natural fuels.
Biomass is another carbonaceous material that can also be converted to synthetic
fuels—the fermentation of grain to produce alcohol is the best-known example. Wood is also
an abundant and accessible source of bio-energy and the procedures for the gasification of
cellulosic materials have much in common with the conversion of coal to gas.
Currently, nonconventional oil production is less efficient and some types have a larger
environmental impact relative to conventional oil production. Nonconventional types of
production include: tar sand, coal, oil shale, and biofuels as well as liquid fuels from natural
gas through processes such as the Fischer-Tropsch process. These nonconventional sources
of oil may be increasingly relied upon as fuel for transportation as the price of conventional
petroleum increases and supplies dwindle.
However, conventional sources of liquid fuels from petroleum are currently preferred
because they provide a much higher ratio of extracted energy over energy used in extraction
and refining processes. Technology, such as using steam injection in heavy oil reservoirs
continues to serve as a means of extracting heavy oil while mining serves as the only com-
mercial production of tar sand bitumen.

TABLE 1.2 Differences between Conventional and Nonconventional Oil (see also Table 1.3)

Conventional oil Nonconventional oil
Mobile, low viscosity liquid oil Tar sand—immobile in the natural state,
viscous, near solid
Many wells flow on their own, or otherwise are Must be mined, or heated-decomposed and then
produced by pumping pumped
Wells often produce water that must be Requires up to 3 bbl of water for every barrel of
disposed of oil produced
Nearing “peak oil” Largely untapped resource
High discovery cost; relatively low production Locations known; relatively high production
cost cost
Production quickly ramps up, peaks, and declines Steady production for next 100 years
Reserves primarily outside North America Extensive reserves in United States, Canada,
Venezuela
Often influences foreign policy Allows energy independence