2. OUTLINE
• What Kerogen is
• Composition of Kerogen
• Classification of Kerogen
• Summary and Conclusion
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3. WHAT KEROGEN IS
Defined by solubility:
Organic Matter insoluble in organic solvents because
of the large molecular weight up to several thousand
Daltons
Defined by petroleum:
• Organic Matter capable of producing petroleum
• End result of diagenesis stage during the process of petroleum
formation is conversion of organic matter to kerogen
Extraction method alters kerogen properties: physical,
compositional, and structural!
• Can be mixed with other insoluble OM: tar, asphaltene,
bitumen!
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4. Ingredient for generatingkerogen
• For kerogen to be generated, organic matter must be present in
abundance
• Organic matter is accumulated mostly in a dispersed state in
predominantly clay-sized marine deposits
• It comprises mainly algae and plants, and some animal matter
• However, the type and amount of kerogen generation from organic
matter in a basin depends on:
nature of the organic matter in the sediments
abundance of the organic matter
thermal maturity (degree of cooking by heating) of the
organic matter during burial
nature and type of environment in which the organic matter
accumulated
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5. NOTE!!!
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* The amount of Organic Matter in
source rocks is critical because < 75%
of the Organic Matter is converted to
petroleum.
* Ideally the Organic Matter content of
the source rock should not < 0.5%. If
it is > 50%, however, the rock is
termed an oil shale.
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“The decomposed components of
bacteria, zooplankton (esp.
foraminifers & crustaceans),
macro benthos, etc along with
that from primary producers (i.e.
molecules derived from proteins,
carbohydrates, lipids, lignin)
form the organic matter that is
found in sediment” (Armstrong,
2010)
7. COMPOSITION OF KEROGEN
• Organic matter is divided into:
1. Humic OM: results in the formation of coal & gas.
2.Sapropelic OM: gives rise to liquid & gaseous HCs.
• On average, the composition of organic matter in sediment is as
follows:
40% Proteins
40% Carbohydrates
10% Lipids
10% Lignin
• These materials are supplied by: Trees, Herbaceous plants, Fungi,
Algae, Protozoa, Bacteria, and Faeces
• All of these + Time + Temperature + Pressure = KEROGEN
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16. CLASSIFICATION OF KEROGEN
• The extreme types of disseminated organic matter
correspond to the class of Kerogen formed.
• According to the van Krevelen diagram, kerogens
can be classified based on the ratios of H/C and O/C.
• The different classifications include:
Type I kerogen
Type II kerogen
Type III kerogen
Type IV kerogen
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18. Type I kerogen or Liptinite
• Rich in lipids particularly aliphatic chains with derivates of oils, fats, &
waxes
• Derived from algae present in fresh water lakes & lagoons.
• Abundant in lacustrine source rocks.
• High proportion of H:C ratio (1.6- 1.8) and low O:C ratio (0.06)
• Usually with the exception of a few algae (e.g. Botryococcus sp.) most
of the organic matter is unrecognizable. The prolific oil shales of
Colorado, Utah, Wyoming (Green River shales) seem to result from a
combination of both algae and mirobial lipids.
• Oil prone; yields high (up to 80%).
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20. Type II kerogen or Exinite
• Most prolific global source rocks
• Rich in lipid
• It is an admixture of
i. Marine material - phytoplanktons , zooplanktons,
algae
ii. Terrestrial (plant) material- spores, pollen, and
cuticle
• Its assemblages dominate in the marine source rocks e.g.
Kimmeridge Clay Fm (NS), Akata Fm (ND)
• Intermediate H:C (about 1.3) & intermediate O:C (0.1)
• Oil & gas prone; yields 40—60%
• Sulphur, where present, influences the timing and rate of
maturation of Type II kerogen.
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22. Type III kerogen (or Vitrinite)
• Rich in lignin derived from woody land plant debris
• The debris occurs abundantly in coals
• Low H:C ratio (< 1.0) & high O:C ratio (0.15)
• Low yield for oil but gas prone
• Low in aliphatic compounds but rich in aromatic compounds
• Example of vitrinite-dominated source rocks include the
Carboniferous Coal Measures of the southern North Sea basin
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23. Type IV kerogen (or Inertinite)
• High in carbon and very low in hydrogen
• Often termed “dead-carbon”
• No effective potential to generate petroleum
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