Kerogen

Kerogen is the organic polymeric material of which with increasing geological sinking and heating hydrocarbons are formed. It occurs in sedimentary rocks in the form of finely divided organic macerals and is by far the most common form of organic carbon in the Earth's crust. It is insoluble in organic solvents, non-oxidizing acid (HCl and HF) and alkali. Kerogen is differentiated into four types of macerals:

Type 1 kerogen ( liptinite - type)

Liptinite is relatively rare and has a high oil production potential, at low maturity a high H / C ratio (> 1.5 ) and low O / C ratio (< 0.1 ). In its composition it has high contributions of lipid substances from algae material and bacterial residues, whereas little aromatics and NSO components. In fine-grained marine and lacustrine muds it is formed as oil shale.

Examples: Green River Formation oil shales of Messel, Swabian Posidonienschiefer.

Type 2 kerogen ( Exinit type)

Exinit is the most widely used kerogen with an average H / C ratio ( 0.8-1.5 ) and average O / C ratios. It contains a lot of aromatic compounds and carboxylic acids and up to 8 to 14 % sulphidic sulfur.

Marine sediments from autochthonous phytoplankton, zooplankton and bacterial material that were deposited under reducing conditions. In part it may also allochthonous spores, pollen and resins of higher plants on the mainland.

Kerogens this type form oil, are often due to their wide distribution, the sources of large oil and gas fields.

Examples: Paris Basin.

Type 3 kerogen ( vitrinite type)

The vitrinite type has a low H / C ratio and a high O / C ratio at low maturity. It contains many polyaromatics, carboxylic acids and ketones. Ester compounds are completely absent. Aliphatic groups are - if at all - only available in methyl and other short-chain groups. Long chains derived from waxes and cutin of higher plants.

Sources are generally higher plants, it often contains woody plant remains. It is very similar in its behavior with increasing sinking coal. It is a poor producer of oil and gas producer a reasonable (especially methane).

Examples: Douala Basin.

Type 4 kerogen ( Inertit type)

Kerogen is composed primarily of this black opaque particles of almost pure carbon, in the form of Inertit. Since it can not form hydrocarbons, it is often not considered to be true kerogen. It arises in terrestrial environments from highly oxidized material of higher plants.