Oil shale differs from coal whereby the organic matter in shales has a higher atomic
Hydrogen to Carbon ratio. Coal also has an organic to inorganic matter ratio of more
than 4,75 to 5 while as oil shales have a higher content of sedimentary rock. Sources
estimate the world reserves of Oil Shales at more than 2,5 trillion barrels.
Oil shales are thought to form when algae and sediment deposit in lakes, lagoons and
swamps where an anaerobic (oxygen free) environment prevent the breakdown of
organic matter, thus allowing it to accumulate in thick layers. Thet is later covered
with overlying rock to be baked under high temperature and pressure. However heat
and pressure was lower than in oil and gas reservoirs. The shale can be strip mined
and processed with distillation. Extraction with fracturing and heating is still
relatively unproven. Companies are experimenting with direct electrical heating
rather than e.g. steam injection. Extraction cost is currently around 25-30 USD per
barrel.
3.8.4 Coal, Coal Gasification and Liquefaction
Coal is similar in origin to oil shales but typically formed from anaerobic decay of
peat swamps relatively free from nonorganic sediment deposits, reformed by heat
and pressure. To form a 1 meter thick coal layer, as much as 30 meters of peat was
originally required. Coal can vary from relatively pure carbon to carbon soaked with
hydrocarbons, sulfur etc.
It has been clear for decades that synthetic oil could be created from coal. Coal
gasification will transform coal into e.g. methane. Liquefaction such as the Fischer-
Tropsch process will turn methane into liquid hydrocarbons. (Typically on the form
CnH2n+2 )
In addition, coal deposits contain large amounts of methane, referred to as coal bed
methane. It is more difficult to produce than normal natural gas (which is also
largely methane), but could add as much as 5-10% to natural gas proven reserves.
3.8.5 Methane Hydrates
Methane hydrates are the most recent form of
unconventional natural gas to be discovered and
researched. These formations are made up of a
lattice of frozen water, which forms a sort of cage
around molecules of methane. Hydrates were first
discovered in permafrost regions of the Arctic and
have been reported from most deepwater
continental shelves tested. The methane can