ORIGIN OF PETROLEUM
There are two basic schools of thought surrounding the formation of petroleum deep
within the earth’s strata. There is the more widely accepted organic theory and the not so
popular inorganic theory.
Inorganic Theories
Deep seated terrestrial hypothesis
From as early as 1877, Dmitri Mendele'ev, a Russian who developed the periodic table,
postulated an inorganic origin when it became apparent that there were widespread
deposits of petroleum throughout the world. He reasoned that metallic carbides deep
within Earth reacted with water at high temperatures to form acetylene (C2H2). This
acetylene condensed to form heavier hydrocarbons. This reaction can be easily performed
under laboratory conditions.
This theory was modified by Berthelot in 1860 and by Mendele'ev in 1902. Their theory
was that the mantle of the earth contained iron carbide which would react with
percolating water to form methane:
FeC2 + 2H2O = CH4 + FeO2
The problem with this theory is the lack of evidence for the existence of iron carbide in
the mantle. These theories are referred to as the deep-seated terrestrial hypothesis.
Extraterrestrial hypothesis.
In 1890, Sokoloff proposed a cosmic origin for petroleum. His theory was that
hydrocarbons precipitated as rain from original nebular matter from which the solar
system was formed. The hydrocarbons were then ejected from earth's interior onto
surface rocks.
Interest in this inorganic theory heightened in the 20th Century as a result of two
discoveries: The existence of carbonaceous chondrites (meteorites) and the discovery that
atmospheres containing methane exists for some celestial bodies such as Saturn, Titan,
Jupiter. The only known source for methane would be through inorganic reactions.
It has been postulated that the original atmosphere of earth contained methane, ammonia,
hydrogen and water vapor which could result is the creation of an oily, waxy surface
layer that may have been host to a variety of developing prebiotic compounds including
the precursors of life as a result of photochemical reactions (due to UV radiation).
The discovery (Mueller, 1963) of a type of meteorite called carbonaceous chondrites, also
led to a renewed interest in an inorganic mechanism for creating organic compounds.
Chondritic meteorites contain greater than 6% organic matter (not graphite) and traces of
various hydrocarbons including amino acids.
The chief support of an inorganic origin is that the hydrocarbons methane, ethane,
acetylene, and benzene have repeatedly been made from inorganic sources. For example,
congealed magma has been found on the Kola Peninsula in Russia (Petersil'ye, 1962)
containing gaseous and liquid hydrocarbons (90% methane, traces of ethane, propane,
isobutane). Paraffinic hydrocarbons have also been found in other igneous rocks (Evans,
Morton, and Cooper, 1964).
Problems with inorganic hypotheses.
Firstly, there is no direct evidence that will show whether the source of the organic
material in the chondritic meteorites is the result of a truly inorganic origin or was in an
original parent material which was organically created. Similar reasoning applies to other
celestial bodies.
Secondly, there is no field evidence that inorganic processes have occurred in nature, yet
there is mounting evidence for an organic origin.
And thirdly, there should be large amounts of hydrocarbons emitted from volcanoes,
congealed magma, and other igneous rocks if an inorganic origin is the primary
methodology for the creation of hydrocarbons. Gaseous hydrocarbons have been
recorded (White and Waring, 1963) emanating from volcanoes, with methane (CH4) the
most common. Volumes are generally less than 1%, but as high as 15% have been
recorded. But the large pools are absent from igneous rocks. Where commercial
accumulations do occur, they are in igneous rocks that have intruded into or are overlain
by sedimentary materials; in other words, the hydrocarbons probably formed in the
sedimentary sequence and migrated into the igneous material (more on this later when we
discuss traps).
Conclusion: There are unquestioned instances of indigenous magmatic oil, but the
occurrences are rare and the volumes of accumulated oil (pools) are low. Other
problematic issues: Commercial accumulations are restricted to sedimentary basins,
petroleum seeps and accumulations are absent from igneous and metamorphic rocks, and
gas chromatography can fingerprint the organic matter in shales to that found in the
adjacent pool. Thus current theory holds that most petroleum is formed by the thermal
maturation of organic matter - An Organic Origin generated the vast reserves (pools) of
oil and gas.
https://www.youtube.com/watch?v=SO2kbie9DtE
There are two basic schools of thought surrounding the formation of petroleum deep
within the earth’s strata. There is the more widely accepted organic theory and the not so
popular inorganic theory.
Inorganic Theories
Deep seated terrestrial hypothesis
From as early as 1877, Dmitri Mendele'ev, a Russian who developed the periodic table,
postulated an inorganic origin when it became apparent that there were widespread
deposits of petroleum throughout the world. He reasoned that metallic carbides deep
within Earth reacted with water at high temperatures to form acetylene (C2H2). This
acetylene condensed to form heavier hydrocarbons. This reaction can be easily performed
under laboratory conditions.
This theory was modified by Berthelot in 1860 and by Mendele'ev in 1902. Their theory
was that the mantle of the earth contained iron carbide which would react with
percolating water to form methane:
FeC2 + 2H2O = CH4 + FeO2
The problem with this theory is the lack of evidence for the existence of iron carbide in
the mantle. These theories are referred to as the deep-seated terrestrial hypothesis.
Extraterrestrial hypothesis.
In 1890, Sokoloff proposed a cosmic origin for petroleum. His theory was that
hydrocarbons precipitated as rain from original nebular matter from which the solar
system was formed. The hydrocarbons were then ejected from earth's interior onto
surface rocks.
Interest in this inorganic theory heightened in the 20th Century as a result of two
discoveries: The existence of carbonaceous chondrites (meteorites) and the discovery that
atmospheres containing methane exists for some celestial bodies such as Saturn, Titan,
Jupiter. The only known source for methane would be through inorganic reactions.
It has been postulated that the original atmosphere of earth contained methane, ammonia,
hydrogen and water vapor which could result is the creation of an oily, waxy surface
layer that may have been host to a variety of developing prebiotic compounds including
the precursors of life as a result of photochemical reactions (due to UV radiation).
The discovery (Mueller, 1963) of a type of meteorite called carbonaceous chondrites, also
led to a renewed interest in an inorganic mechanism for creating organic compounds.
Chondritic meteorites contain greater than 6% organic matter (not graphite) and traces of
various hydrocarbons including amino acids.
The chief support of an inorganic origin is that the hydrocarbons methane, ethane,
acetylene, and benzene have repeatedly been made from inorganic sources. For example,
congealed magma has been found on the Kola Peninsula in Russia (Petersil'ye, 1962)
containing gaseous and liquid hydrocarbons (90% methane, traces of ethane, propane,
isobutane). Paraffinic hydrocarbons have also been found in other igneous rocks (Evans,
Morton, and Cooper, 1964).
Problems with inorganic hypotheses.
Firstly, there is no direct evidence that will show whether the source of the organic
material in the chondritic meteorites is the result of a truly inorganic origin or was in an
original parent material which was organically created. Similar reasoning applies to other
celestial bodies.
Secondly, there is no field evidence that inorganic processes have occurred in nature, yet
there is mounting evidence for an organic origin.
And thirdly, there should be large amounts of hydrocarbons emitted from volcanoes,
congealed magma, and other igneous rocks if an inorganic origin is the primary
methodology for the creation of hydrocarbons. Gaseous hydrocarbons have been
recorded (White and Waring, 1963) emanating from volcanoes, with methane (CH4) the
most common. Volumes are generally less than 1%, but as high as 15% have been
recorded. But the large pools are absent from igneous rocks. Where commercial
accumulations do occur, they are in igneous rocks that have intruded into or are overlain
by sedimentary materials; in other words, the hydrocarbons probably formed in the
sedimentary sequence and migrated into the igneous material (more on this later when we
discuss traps).
Conclusion: There are unquestioned instances of indigenous magmatic oil, but the
occurrences are rare and the volumes of accumulated oil (pools) are low. Other
problematic issues: Commercial accumulations are restricted to sedimentary basins,
petroleum seeps and accumulations are absent from igneous and metamorphic rocks, and
gas chromatography can fingerprint the organic matter in shales to that found in the
adjacent pool. Thus current theory holds that most petroleum is formed by the thermal
maturation of organic matter - An Organic Origin generated the vast reserves (pools) of
oil and gas.
https://www.youtube.com/watch?v=SO2kbie9DtE
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