PETROLUEM GEOLOGYAMOO K

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PETROLUEM GEOLOGY

GEOL 436

AMOO K. OBAFEMI 10234452

1ST FEBRUARY, 2010

PROFESSOR ATTA-PETERS

ORIGIN OF PETROLUEM; BIOGENIC OR ABIOGENIC

ABSTRACT

In the simplest terms, biogenic origin of petroleum refers to the production of kerogen as a result

of great change to the remains of ancient plants and animals. Abiogenic origin is, as the name

suggests the reverse and argues thatpetroleum was formed from deep carbon deposits, perhaps

dating to the formation of the Earth. The presence ofmethane on Saturn's moon Titan is cited as

evidence supporting the formation of hydrocarbons without biology, and petroleum may

originate from carbon-bearing fluids that migrate upward from the mantle. This is in sharp

contrast to the widely accepted explanation for the formation of oil and gas deposits that they are

the remains of plant and animal life that died millions of years ago and were compressed by heat

and pressure over millions of years.

Proponents of the abiogenic origin argue that formation of methane and hydrocarbon

gases have been found within the earth, although not in commercial quantities but made a strong

case when American scientist Thomas Gold discovered thermophile bacteria in the Earth's crust

explaining the existence of certainbiomarkers in extracted petroleum, as cited in his publication

the deep hot biosphere. Gold explained that hydrogen and carbon, under high temperatures and

pressures found in the mantle during the formation of the Earth, form hydrocarbon molecules

which have gradually leaked up to the surface through cracks in rocks. The organic materials

which are found in petroleum deposits are easily explained by the metabolism of bacteria which

have been found in extreme environments similar to Earth's mantle. These hyperthermophiles, or

bacteria which thrive in extreme environments, have been found in hydrothermal vents, at the


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bottom of volcanoes, and in places where scientists formerly believed life was not possible. He

also argues that the mantle contains vast numbers of these bacteria.

Berthelot in 1866 suggested that carbides are the primary source of petroleum and the reaction of

alkali metals with carbonates formed these carbides which then react with water, mostly

groundwater with increased pressure and temperature to form petroleum, this was seconded by

the Russian chemist Mendeleev. Others advanced astrophysical evidence as presented by

Kudryavtsev who suggested the presence of CH3 in the sun are also present id deep-seated zones

from the earth by a direct synthesis of C and H. these penetrates into cooler parts of the mantle

and combines with each other forming petroleum-like compounds.

These scientists dismiss the idea that oil is a finite resource of biological origin and that given

enough time, the earths finite crustal oil and gas reservoirs get replenished through diffusion

from the mantles supposedly infinite source to the surface.

If this is true; there could be vast deposits of oil and gas yet to be discovered miles below the

crust of virtually unlimited supply.

The biogenic origin enjoys lots of support, especially from western scientists. It suggests that

petroleum and natural gas are the products of decomposition of ancient biological lives over

geological time. Coal beds are the products of ancient vegetative deposition and decomposition

over millions of years, while the accumulation of sediment-buried marine organisms on the

seafloor forms oil and gas deposits, anaerobic bacterial decomposition is stopped at temperatures

where life is no longer possible.

Western biogenic proponents have argued that the optical activity of petroleum and synthesis of

optical active compounds is said to take place only by living organisms. Also, the similarity in

structure between some petroleum hydrocarbons and organic compounds synthesized by living

organisms as well as the reported presence of pristine and phytane in many crudes could as muchsupport the biogenic origin of petroleum.

Interestingly; there are those who believe that petroleum hydrocarbons are both biogenic and

abiogenic (dual origin), although the latter being very much older (primordial formation). They

argue that the indication of biogenesis are observed in young oils, less evidenced in middle age


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oils and completely absent in older crudes. Primitive material formed from the earth is believed

to contain a small percentage of high molecular weight hydrocarbons just like some meteorites

now observed. These hydrocarbons were also believed to have undergone thermal cracking

which then flows through porous strata picking up some biogenic quantities in the process.

REFERENCES

Duplex origin of petroleum, pg 394

Jan Willem Jurg , The mechanism of the generation of petroleum , proefschrift.

Levin. B.U, Organic compounds in the solar system, problems of petroleum origin, scientific

thought press, pg 178, 1966.

N.A Kudryavstev, Against the organic hypothesis of petroleum origins, Petroleum economy, p

17,1957.

www.wikipedia.com/abiogenic petroleum.

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PETROLUEM GEOLOGYAMOO K