Oil shale

In short

Oil shale is a fine-grained sedimentary rock that contains kerogen, a solid organic matter. The kerogen has not yet turned into petroleum; when the rock is heated to 450–500 °C without oxygen it breaks down into oil, gas and a solid residue. Rich types can be burned directly. It is not the same as the “tight oil” shales, whose pores already hold liquid petroleum.

Photos

How to recognise it

1. 1

   It ranges in colour from brown through grey to black, is finely layered with a dull surface, and splits into sheets.

2. 2

   It gives off an oily, tarry smell when scratched or heated, and a knife scratches it easily.

3. 3

   It often does not fizz in vinegar or dilute acid, which can tell it apart from limestone.

4. 4

   It is lighter than ordinary shale of the same size; the more organic matter it holds, the lower its density.

Myths and misconceptions

• MythOil shale contains liquid oil that is pumped out by drilling.

  FactOil shale holds not liquid oil but a solid organic matter called kerogen; oil appears only when the rock is heated to 450–500 °C. The oil carried in the pores of some shales is called tight oil.

• MythBituminous schist is a kind of schist.

  FactDespite the name it is not a schist changed by heat and pressure, but a sedimentary shale rich in organic matter. In Türkiye “bitümlü şist”, “bitümlü şeyl” and “petrollü şeyl” are names of the same rock.

Did you know?

Where is it found?

• Green River Formation, Piceance Basin, Colorado, USA · Major depositEocene lake deposits spread across Colorado, Utah and Wyoming and make up the world's largest oil shale deposit. The Colony project near Parachute was cancelled in 1982.
• Ida-Viru County, north-east Estonia · Major depositThe Ordovician kukersite is mined here; mining began in 1916 and shale oil production started at Kohtla-Järve in 1921. The Narva power stations are the world's two largest oil-shale-fired plants.
• Fushun, Liaoning, China · Known localityCommercial-scale shale oil production from oil shale began in 1928; “Fushun-type” retorts became an industry standard.
• Irati Formation, Paraná Basin, Brazil · Known localityAn Early Permian black shale; in Brazil oil is produced from oil shale by the Petrosix process. The same beds are also famous for their Mesosaurus fossils.
• Autun, Burgundy, France · Historic sourceCommercial oil shale mining began in the area in 1837, regarded as the start of the modern oil shale industry.
• Messel Pit, Hesse, Germany · Known localityA former pit mined for brown coal and then oil shale from 1859 to 1971; more than 1,400 kinds of plants, fungi and animals have been documented in its Middle Eocene shale. A UNESCO World Heritage Site since 1995.
• Kimmeridge Bay, Dorset, England · Known localityThe Late Jurassic Kimmeridge Clay is the main source rock of the North Sea oil fields; its oily beds are said to have been burned as fuel in the past.
• Göynük (Himmetoğlu and Hatıldağ fields), Bolu, Türkiye · Major depositThe Himmetoğlu oil shale is Neogene in age and is described as the best-quality oil shale deposit in Türkiye; the Hatıldağ field is in the same district. Attempts, together with Germany, to produce oil from the oil shales around Bolu were never completed.
• Beypazarı, Ankara, Türkiye · Known localityOne of the fields where MTA has surveyed oil shale.
• Seyitömer, Kütahya, Türkiye · Known localityA reserve of about one billion tonnes of oil shale has been reported; its calorific value is very low (150–3,000 kcal/kg) and its mineral content high, which makes it hard to burn.
• Ereğli (Konya)–Bor (Niğde) basin, Türkiye · Known localityMTA drilling cut oil shale beds averaging 40 m thick in Neogene lake deposits, and a potential reserve of about 8 billion tonnes has been calculated. TPAO's 2,500 m well found no economic oil.

Locations are approximate to protect sites. Red dots mark places in Türkiye. Open in the big map →