Kerogens are chemical compounds that make up a portion of the organic matter in sedimentary rocks. They are insoluble in normal organic solvents because of thier huge molecular weight (upwards of 1,000). The soluble portion is known as bitumen. Each kerogen molecule is unique because it is formed by the random combination of numerous monomers. A chemical compound is a chemical substance formed from two or more elements, with a fixed ratio determining the composition. ... Bitumen Bitumen is a category of organic liquids that are highly viscous, black, sticky and wholly soluble in carbon disulfide. ...

Kerogens are the precursors to hydrocarbons (fossil fuels), and are also the material that forms oil shales. Hydrocarbons are refined at oil refineries and chemical plants In chemistry, a hydrocarbon is any chemical compound that consists only of the elements carbon (C) and hydrogen (H). ... Coal rail cars in Ashtabula, Ohio Fossil fuels, also known as mineral fuels, are hydrocarbon-containing natural resources such as coal, oil and natural gas. ... Oil shale is a general term applied to a group of fine black to dark brown shales rich enough in bituminous material (called kerogen) to yield petroleum upon distillation. ...

Formation

(for kerogens deposited in marine environments - the most significant form for petroleum)

Types

Labile kerogen breaks down to form heavy hydrocarbons (i.e. oils), refractory kerogen breaks down to form light hydrocarbons (i.e. gases) and inert kerogen forms graphite. Graphite (named by Abraham Gottlob Werner in 1789, from the Greek γραφειν: to draw/write, for its use in pencils) is one of the allotropes of carbon. ...

A Van Krevelen diagram is one example of classifying kerogens, where they tend to form groups when the ratios of hydrogen to carbon and oxygen to carbon are compared.

Type I

• containing alginite and amorphous organic matter (AMO)
• Hydrogen:Carbon ratio > 1.25
• Oxygen:Carbon ratio < 0.15
• Shows great tendency to readily produce liquid hydrocarbons, but its occurrence is extremely limited and does not warrant the attention given to it.
• It derives principally from lacustrine algae and forms only in anoxic lakes and several other unusual marine environments
• Has few cyclic or aromatic structures
• Formed mainly from proteins and lipids

Alginite is a type of kerogen. ... Alginite is a component of some types of kerogen alongside amorphous organic matter. ...

Type II

• Hydrogen:Carbon ratio < 1.25
• Oxygen:Carbon ratio 0.03 to 0.18
• Tend to produce a mix of gas and oil.
• Several types: exinite, cutinite, resinite, and liptinite
• Exinite: formed from pollen and spores
• Cutinite: formed from terrestrial plant cuticle
• Resinite: terrestrial plant resins, animal decomposition resins
• Liptinite: formed from terrestrial plant lipids (hydrophobic molecules that are soluble in organic solvents) and marine algae

They all have great tendencies to produce petroleum and are all formed from lipids deposited under reducing conditions.

Type II-Sulfur

• Similar to Type II but high in sulfur.

General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Atomic mass 32. ...

Type III

• Hydrogen:Carbon ratio < 1
• Oxygen:Carbon ratio 0.03 to 0.3
• Material is thick, resembling wood or coal.
• Tends to produce coal and gas
• Has very low hydrogen because of the extensive ring and aromatic systems

Kerogen Type III is formed from terrestrial plant matter that is lacking in lipids or waxy matter. It forms from cellulose, the carbohydrate polymer that forms the rigid structure of terrestrial plants, lignin, another carbohydrate polymer (polysaccharide) that binds the strings of cellulose together, and terpenes and phenolic compounds in the plant. Figure 1: Structure of a Lipid. ... Cellulose (C6H10O5)n is a long-chain polymer polysaccharide carbohydrate, of beta-glucose. ... Lignin is a chemical compound that is an integral part of the cell walls of some cells, e. ... Terpenes are a class of hydrocarbons, produced by many plants, particularly conifers. ... Phenol, also known under the old name carbolic acid, is a colorless crystalline solid with a typical sweet tarry odor. ...

Most of the biomass that eventually becomes petroleum is contributed by the bacteria and protists that decompose the primary matter, not the primary matter itself. However, the lignin in this kerogen decomposes to form phenolic compounds that are toxic to bacteria and protists. Without this extra input, it will only become methane and/or coal. Pumpjack pumping an oil well near Sarnia, Ontario Petroleum (from Greek petra – rock and elaion – oil or Latin oleum – oil ), crude oil, sometimes colloquially called black gold or Texas Tea, is a thick, dark brown or greenish liquid. ... R-phrases S-phrases , , , Flash point −188 °C Autoignition temperature 537 °C Explosive limits 5–15% Supplementary data page Structure and properties Thermodynamic data Spectral data UV, IR, NMR, MS Related compounds Related alkanes Ethane Propane Related compounds Methanol Chloromethane Except where noted otherwise, data are given for materials in... Coal is a fossil fuel extracted from the ground by underground mining or open-pit mining (strip mining). ...

Type IV (residue)

• Hydrogen:Carbon < 0.5

Type IV kerogen contains mostly decomposed organic matter in the form of polycyclic aromatic hydrocarbons. They have no potential to produce hydrocarbons. Polycyclic aromatic hydrocarbons (PAHs) are chemical compounds that consist of fused aromatic rings and do not contain heteroatoms or carry substituents. ...

Origin of material

Terrestrial material

The type of material is difficult to determine but several apparent patterns have been noticed.

• Ocean or lake material often meet kerogen type III or IV classifications.
• Ocean or lake material deposited under anoxic conditions often form kerogens of type I or II.
• Most higher land plants produce kerogens of type III or IV.
• Some coal contains type II kerogen.

Decline of oxygen saturation to anoxia, measured during the night in Kiel Fjord, Germany. ... Coal is a fossil fuel extracted from the ground by underground mining or open-pit mining (strip mining). ...

Extraterrestrial material

• Carbonaceous chondrite meteorites contain kerogen-like components. Such material is believed to have formed the terrestrial planets.
• Kerogen materials have been detected in interstellar clouds and dust around stars.

Some carbonaceous chondrites. ... A meteorite is a small extraterrestrial body that impacts the Earths surface. ... A terrestrial planet or telluric planet is a planet which is primarily composed of silicate rocks. ...

External links

• European Association of Organic Geochemists
• Organic Geochemistry

See also: petroleum geology. Petroleum geology is a term used to refer to the specific set of geological disciplines that are applied to the search for hydrocarbons (oil exploration). ...