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Kerogen
 
 
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Kerogen is a mixture of organic
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
 chemical compound
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
s that make up a portion of the organic matter in sedimentary rock
Sedimentary rock

Sedimentary rock is one of the three main Rock types . Sedimentary rock is formed by deposition and consolidation of mineral and organic material and from precipitation of minerals from solution....
s. It is insoluble in normal organic
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
 solvent
Solvent

A solvent is a liquid or gas that dissolves a solid, liquid, or gaseous solute, resulting in a solution.The most common solvent in everyday life is water....
s because of the huge molecular weight
Molecular mass

The molecular mass of a chemical compound, frequently referred by the older term molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u ....
 (upwards of 1,000 Daltons
Atomic mass unit

The unified atomic mass unit , or dalton or, sometimes, universal mass unit, is a Units of measurement of mass used to express atomic weight and molecular masses....
) of its component compounds. The soluble portion is known as bitumen
Bitumen

Bitumen is a mixture of organic compounds liquids that are highly viscous, black, sticky, entirely soluble in carbon disulfide, and composed primarily of highly condensed polycyclic aromatic hydrocarbons....
. When heated to the right temperatures in the Earth's crust
Crust (geology)

In geology, a crust is the outermost solid shell of a planet or moon, which is chemically distinct from the underlying mantle . Crusts of Earth , our Moon, Mercury , Venus, and Mars have been generated largely by igneous processes, and these crusts are richer in incompatible elements than their respective mantle s....
, (oil window ca. 60°-120°C, gas window ca.120°-150°C) some types of kerogen release crude oil or natural gas
Natural gas

Natural gas is a gas consisting primarily of methane. It is found associated with fossil fuels, in coal beds, as methane clathrates, and is created by methanogenic organisms in marshes, bogs, and landfills....
, collectively known as hydrocarbon
Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. With relation to chemical terminology, aromatic hydrocarbons or arenes, alkanes, alkenes and alkyne-based compounds composed entirely of carbon or hydrogen are referred to as "pure" hydrocarbons, whereas other hydrocarbons with bonded com...
s (fossil fuel
Fossil fuel

Fossil fuels or mineral fuels are fossil source fuels, that is, carbon or hydrocarbons found in the earth?s Crust .Fossil fuel range from volatile materials with low carbon:hydrogen ratios like methane, to liquid petroleum to nonvolatile materials composed of almost pure carbon, like anthracite coal....
s).






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Kerogen is a mixture of organic
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
 chemical compound
Chemical compound

A chemical compound is a Chemical substance consisting of two or more different chemical element Chemical bond together in a fixed mass ratio that can be split into simpler substances....
s that make up a portion of the organic matter in sedimentary rock
Sedimentary rock

Sedimentary rock is one of the three main Rock types . Sedimentary rock is formed by deposition and consolidation of mineral and organic material and from precipitation of minerals from solution....
s. It is insoluble in normal organic
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
 solvent
Solvent

A solvent is a liquid or gas that dissolves a solid, liquid, or gaseous solute, resulting in a solution.The most common solvent in everyday life is water....
s because of the huge molecular weight
Molecular mass

The molecular mass of a chemical compound, frequently referred by the older term molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u ....
 (upwards of 1,000 Daltons
Atomic mass unit

The unified atomic mass unit , or dalton or, sometimes, universal mass unit, is a Units of measurement of mass used to express atomic weight and molecular masses....
) of its component compounds. The soluble portion is known as bitumen
Bitumen

Bitumen is a mixture of organic compounds liquids that are highly viscous, black, sticky, entirely soluble in carbon disulfide, and composed primarily of highly condensed polycyclic aromatic hydrocarbons....
. When heated to the right temperatures in the Earth's crust
Crust (geology)

In geology, a crust is the outermost solid shell of a planet or moon, which is chemically distinct from the underlying mantle . Crusts of Earth , our Moon, Mercury , Venus, and Mars have been generated largely by igneous processes, and these crusts are richer in incompatible elements than their respective mantle s....
, (oil window ca. 60°-120°C, gas window ca.120°-150°C) some types of kerogen release crude oil or natural gas
Natural gas

Natural gas is a gas consisting primarily of methane. It is found associated with fossil fuels, in coal beds, as methane clathrates, and is created by methanogenic organisms in marshes, bogs, and landfills....
, collectively known as hydrocarbon
Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. With relation to chemical terminology, aromatic hydrocarbons or arenes, alkanes, alkenes and alkyne-based compounds composed entirely of carbon or hydrogen are referred to as "pure" hydrocarbons, whereas other hydrocarbons with bonded com...
s (fossil fuel
Fossil fuel

Fossil fuels or mineral fuels are fossil source fuels, that is, carbon or hydrocarbons found in the earth?s Crust .Fossil fuel range from volatile materials with low carbon:hydrogen ratios like methane, to liquid petroleum to nonvolatile materials composed of almost pure carbon, like anthracite coal....
s). When such kerogens are present in high concentration in rocks such as shale
Shale

Shale is a fine-grained sedimentary rock whose original constituents were clay minerals or muds. It is characterized by thin laminae breaking with an irregular curving fracture, often splintery and usually parallel to the often-indistinguishable bedding plane....
, and have not been heated to a sufficient temperature to release their hydrocarbons, they may form oil shale
Oil shale

The fine-grained sedimentary rock known as oil shale contains significant amounts of kerogen , from which technology can extract liquid hydrocarbons....
 deposits.

As kerogen is a mixture of organic material, rather than a specific chemical; it cannot be given a chemical formula. Indeed its chemical composition can vary distinctively from sample to sample. Kerogen from the Green River Formation
Green River Formation

The Green River Formation is an Eocene geologic formation that records the sedimentation in a series of intermountain lakes. The sedimentary layers were formed in a large area of interconnecting lakes, named for the present-day Green River , a tributary of the Colorado River....
 oil shale deposit of western North America
North America

North America is the northern continent of the Americas, situated in the Earth's northern hemisphere and almost totally in the western hemisphere....
 contains elements in the proportions C 215 : H 330 : O 12 : N 5 : S 1.

Types

Labile kerogen breaks down to form heavy hydrocarbon
Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. With relation to chemical terminology, aromatic hydrocarbons or arenes, alkanes, alkenes and alkyne-based compounds composed entirely of carbon or hydrogen are referred to as "pure" hydrocarbons, whereas other hydrocarbons with bonded com...
s (i.e. oil
Oil

An oil is a chemical substance that is in a viscosity liquid state at room temperature or slightly warmer, and is both hydrophobic and lipophilic ....
s), refractory
Refractory

A refractory material is one that retains its strength at high temperatures. ASTM International C71 defines refractories as "non-metallic materials having those chemical and physical properties that made them applicable for structures, or as components of systems, that are exposed to environments above 1000 ?F "....
 kerogen breaks down to form light hydrocarbons (i.e. gases), and inert
Inert

In English, to be inert is to be in a state of doing little or nothing....
 kerogen forms graphite
Graphite

The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Greek language ??afe?? : "to draw/write", for its use in pencils, where it is commonly called lead, as distinguished from the actual metallic element lead....
.

A Van Krevelen diagram
Van Krevelen diagram

Van Krevelen diagrams are a graphical-statistical method that cross-plots the oxygen:carbon and hydrogen:carbon ratios of petroleum....
 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
    Alginite

    Alginite is a component of some types of kerogen alongside amorphous organic matter. Alginite consists of organic-walled marine microfossils, distinct from inorganic -walled microfossils that comprise diatomaceous earth....
    , amorphous organic matter, cyanobacteria
    Cyanobacteria

    Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis....
    , freshwater
    Freshwater

    Freshwater is a word that refers to bodies of water such as ponds, lakes, rivers and streams containing low concentrations of dissolved salts and other total dissolved solids....
     algae
    Algae

    Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds....
    , and land plant resin
    Resin

    Resin is a hydrocarbon secretion of many plants, particularly Pinophyta. It is valued for its chemical constituents and uses, such as varnishes and adhesives, as an important source of raw materials for organic synthesis, or for incense and perfume....
    s (AMO)
  • Hydrogen
    Hydrogen

    Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
    :Carbon
    Carbon

    Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
     ratio > 1.25
  • Oxygen
    Oxygen

    Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
    :Carbon ratio < 0.15
  • Shows great tendency to readily produce liquid
    Liquid

    Liquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material....
     hydrocarbons.
  • It derives principally from lacustrine algae and forms only in anoxic
    Anoxic sea water

    Anoxic waters are areas of sea water or fresh water that are depleted of dissolved oxygen. This condition is generally found in areas that have restricted water exchange....
     lakes and several other unusual marine environments
  • Has few cyclic
    Cycloalkane

    Cycloalkanes are types of alkanes which have one or more rings of carbon atoms in the chemical structure of their molecules. Alkanes are types of Organic compound hydrocarbon Chemical compound which have only single chemical bonds in their chemical structure....
     or aromatic
    Aromatic hydrocarbon

    An aromatic hydrocarbon or arene is a hydrocarbon, of which the molecular structure incorporates one or more planar sets of six carbon atoms that are connected by delocalised electrons numbering the same as if they consisted of alternating single and double covalent bonds....
     structures
  • Formed mainly from protein
    Protein

    Proteins are organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid Residue ....
    s and lipid
    Lipid

    Lipids are broadly defined as any fat-soluble , naturally-occurring molecule, such as fats, oils, waxes, cholesterol, sterols, fat-soluble vitamins , monoglycerides, diglycerides, phospholipids, and others....
    s


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
    Exinite

    Formerly, in coal geology, exinite was an umbrella term, used when referring to the finely-ground and macrerated remains, originally formed by spores, pollen, dinoflagellate cysts, leaf cuticles, plant resins and waxes, as found in coal deposits....
    , cutinite, resinite, and liptinite
    • Exinite
      Exinite

      Formerly, in coal geology, exinite was an umbrella term, used when referring to the finely-ground and macrerated remains, originally formed by spores, pollen, dinoflagellate cysts, leaf cuticles, plant resins and waxes, as found in coal deposits....
      : formed from the casings of pollen
      Pollen

      Pollen is a fine to coarse powder consisting of Gametophyte , which produce the male gametes of spermatophyta. A hard coat covering the pollen grain protects the sperm cells during the process of their movement between the stamens of the flower to the pistil of the next flower....
       and spore
      Spore

      In biology, a spore is a reproduction structure that is adapted for biological dispersal and surviving for extended periods of time in unfavorable conditions....
      s
    • Cutinite: formed from terrestrial plant cuticle
      Plant cuticle

      Plant cuticles are a protective waxy covering produced only by the Epidermis of leaf, young shoots and all other aerial plant organs without periderm....
    • Resinite: formed from terrestrial plant resins and animal decomposition resins
    • Liptinite: formed from terrestrial plant lipid
      Lipid

      Lipids are broadly defined as any fat-soluble , naturally-occurring molecule, such as fats, oils, waxes, cholesterol, sterols, fat-soluble vitamins , monoglycerides, diglycerides, phospholipids, and others....
      s (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
Redox

Redox describes all chemical reactions in which atoms have their oxidation number changed.This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane , or it can be a complex process such as the oxidation of sugar in the human body through a ser...
 conditions.

Type II-Sulfur

  • Similar to Type II but high in sulfur
    Sulfur

    Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
    .


Type III

  • Hydrogen:Carbon ratio < 1
  • Oxygen:Carbon ratio 0.03 to 0.3
  • Material is thick, resembling wood
    Wood

    Wood is an organic material; in the strict sense wood is produced as secondary xylem in the stems of woody plants, notably trees but also shrubs, etc....
     or coal
    Coal

    Coal is a readily combustion black or brownish-black sedimentary rock. The harder forms, such as anthracite, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure....
    .
  • 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 lipid
Lipid

Lipids are broadly defined as any fat-soluble , naturally-occurring molecule, such as fats, oils, waxes, cholesterol, sterols, fat-soluble vitamins , monoglycerides, diglycerides, phospholipids, and others....
s or waxy matter. It forms from cellulose
Cellulose

File:Cellulose Sessel.svgCellulose is an organic compound with the chemical formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand ? linked D-glucose units....
, the carbohydrate
Carbohydrate

Carbohydrates or saccharides are the most abundant of the four major classes of biomolecules. They fill numerous roles in living things, such as the storage and transport of energy and structural components ....
 polymer
Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
 that forms the rigid structure of terrestrial plants, lignin
Lignin

Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae....
, a non-carbohydrate polymer formed from phenyl-propane units that binds the strings of cellulose together, and terpene
Terpene

Terpenes are a large and varied class of hydrocarbons, produced primarily by a wide variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium....
s and phenol
Phenol

Phenol, also known as carbolic acid, is a toxic, white crystalline solid with a sweet tarry odor, commonly referred to as a "hospital smell"....
ic compounds in the plant.

Most of the biomass
Biomass

Biomass, as a renewable energy source, refers to living and recently dead biological material that can be used as fuel or for industrial production....
 that eventually becomes petroleum
Petroleum

Petroleum or crude oil is a naturally occurring, flammable liquid found in rock formations in the Earth consisting of a complex mixture of hydrocarbons of various molecular weights, plus other organic compounds....
 is contributed by the bacteria
Bacteria

The Bacteria are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals....
 and protist
Protist

Protists ; eukaryote microorganisms. Historically, protists were treated as the kingdom Protista but this group is no longer recognized in modern taxonomy....
s 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
Methane

Methane is a chemical compound with the molecular formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees....
 and/or coal
Coal

Coal is a readily combustion black or brownish-black sedimentary rock. The harder forms, such as anthracite, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure....
.

Type IV (residue)

  • Hydrogen:Carbon < 0.5


Type IV kerogen contains mostly decomposed organic matter in the form of polycyclic aromatic hydrocarbon
Polycyclic aromatic hydrocarbon

Polycyclic aromatic hydrocarbons are chemical compounds that consist of fused aromatic simple aromatic ring and do not contain heteroatoms or carry substituents....
s. They have no potential to produce hydrocarbons.

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
    Hypoxia (environmental)

    Hypoxia or oxygen depletion is a phenomenon that occurs in aquatic environments as oxygen becomes reduced in concentration to a point detrimental to aquatic organisms living in the system....
     conditions often form kerogens of type I or II.
  • Most higher land plants produce kerogens of type III or IV.
  • Some coal
    Coal

    Coal is a readily combustion black or brownish-black sedimentary rock. The harder forms, such as anthracite, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure....
     contains type II kerogen.


Extraterrestrial material

  • Carbonaceous chondrite
    Carbonaceous chondrite

    Carbonaceous chondrites or C chondrites are a class of chondrite meteorites comprising at least 8 known groups and many ungrouped meteorites....
     meteorite
    Meteorite

    A meteorite is a natural object originating in outer space that survives an impact with the Earth's surface. While in space it is called a meteoroid....
    s contain kerogen-like components. Such material is believed to have formed the terrestrial planet
    Terrestrial planet

    A terrestrial planet, telluric planet, rocky planet or inner planet is a planet that is primarily composed of silicate Rock s....
    s.
  • Kerogen materials have been detected in interstellar clouds and dust
    Interstellar medium

    In astronomy, the interstellar medium is the gas and cosmic dust that pervade interstellar space: the matter that exists between the stars within a galaxy....
     around star
    Star

    A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
    s.


See also

  • Asphaltene
  • Oil shale geology
    Oil shale geology

    Oil shale geology is a branch of geology which studies the formation and composition of oil shales–fine-grained sedimentary rocks containing significant amounts of kerogen, and belonging to the group of sapropel fuels....
  • Petroleum geology
    Petroleum geology

    Petroleum geology refers to the specific set of geological disciplines that are applied to the search for hydrocarbons ....
  • Tholin
    Tholin

    Tholin , is a heteropolymer molecule formed by solar ultraviolet irradiation of simple organic compounds such as methane or ethane. Tholins do not form naturally on modern-day Earth, but are found in great abundance on the surface of icy bodies in the outer solar system....


External links

  • (journal)