OIL YIELD BASICS
For immature oil shales, rock samples are analyzed in the laboratory using a process called Fuscher analysis, giving an oil yield in US gallons per ton of rock. Mature oil shales are analyzed using conventional core analysis coupled with standard geochemical and total organic carbon analysis.
The distinguishing characteristic of an immature "oil shale" is that it contains significant organic carbon but no free oil or gas. This hydrocarbon is immature, not yet transformed into oil by natural processes, and are usually termed "source rocks". Some adsorbed and some free gas may also exist. Immature oil shales require a specialized log analysis model because the Archie saturation model is often inappropriate.
Immature oil shale can be mined on the surface or
at depth and the rock heated in a retort to convert the organic
content to oil. Some valuable by products such as vanadium may
also be extracted, but dry clay, ash, and other minerals are a
serious waste disposal issue. In-situ extraction using
super-heated steam, air, carbon dioxide, or some other heat
transfer system is used to convert the organic carbon to oil.
Collector wells then extract the oil.
CLASSIFYING OIL Shale A useful classification of oil shales was developed by A.C. Hutton. He divided oil shale into three groups based on their deposition environment: terrestrial, lacustrine, and marine, and further by the origin of their organic matter.
Terrestrial oil shales include those composed of lipid-rich organic matter such as resin spores, waxy cuticles, and corky tissue of roots and stems of vascular terrestrial plants commonly found in coal-forming swamps and bogs. Lacustrine oil shales include organic matter derived from algae that lived in fresh, brackish, or saline lakes. Marine oil shales are composed of organic matter derived from marine algae unicellular organisms, and marine dinoflagellates.
1. Cannel coal is brown to black oil shale composed of resins, spores, waxes, and cutinaceous and corky materials derived from terrestrial vascular plants together with varied amounts of vitrinite and inertinite. Cannel coals originate in oxygen-deficient ponds or shallow lakes in peat-forming swamps and bogs.
4. Torbanite, named after Torbane Hill in Scotland, is a black oil shale whose organic matter is composed mainly of telalginite found in fresh- to brackish-water lakes. The deposits are commonly small, but can be extremely high grade.
5. Tasmanite, named from oil-shale deposits in Tasmania, is a brown to black oil shale. The organic matter consists of telalginite derived chiefly from unicellular algae of marine origin and lesser amounts of vitrinite, lamalginite, and inertinite.
6. Kukersite, which takes its name from Kukruse Manor near the town of Kohtla-Järve, Estonia, is a light brown marine oil shale. Its principal organic component is telalginite derived from green algae. Kukersdite is the main type of oil shale in Estonia and westtern Russiaa, and is burned instead of coal to generate electricity in power plants.
OIL Shale IN CANADA Canada produced some shale oil from deposits in New Brunswick in the mid-1800's. The mineral was called Albertite and was originally believed to be a form of coal.
Albert Mines, New Brunswick, in 1850's
Later, the nature of the mineral and its relation to the surrounding oil shale was described correctly. Abraham Gesner used Albertite in his early experiments to distill liquid fuel from coal and solid bitumen. He is credited with the invention of kerosene in 1846, and built a significant commercial distillery to provide lighting oil to replace whale oil in eastern Canada and USA. In the 1880's, shale oil was abandoned as a source of kerosene in favour of distillation from liquid petroleum.
Canada's oil-shale deposits range from
Ordovician to Cretaceous age and include deposits of lacustrine
and marine origin in at least 20 locations across the country.
During the 1980s, a number of the deposits were explored by core
drilling. The oil shales of the New Brunswick Albert Formation,
lamosites of Mississippian age, have the greatest potential for
development. The Albert oil shale averages 100 l/t of shale oil
and has potential for recovery of oil and may also be used for
co-combustion with coal for electric power generation.
The heating value is useful for determining the quality of an
oil shale that is burned directly in a power plant to produce
electricity. Although the heating value of a given oil shale is
a useful and fundamental property of the rock, it does not
provide information on the amounts of shale oil or combustible
gas that would be yielded by retorting (destructive
distillation).
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