Abiogenic petroleum origin
Encyclopedia
Abiogenic petroleum origin is a largely abandoned hypothesis
that was proposed as an alternative to theory of biological petroleum origin. It was relatively popular in the past, but it went largely forgotten at the end of the 20th century after it failed to predict the location of new wells.
The abiogenic hypothesis argues that petroleum
was formed from deep carbon deposits, perhaps dating to the formation of the Earth
. Supporters of the abiogenic hypothesis suggest that a great deal more petroleum exists on Earth than commonly thought, and that petroleum may originate from carbon-bearing fluids that migrate upward from the mantle
. The presence of methane
on Saturn's moon Titan and in the atmospheres of Jupiter, Saturn, Uranus and Neptune is cited as evidence of the formation of hydrocarbons without biology.
The biogenic theory for petroleum was first proposed by Georg Agricola
in the 16th century and various abiogenic hypotheses were proposed in the 19th century, most notably by Alexander von Humboldt
, the Russian chemist Dmitri Mendeleev
and the French chemist Marcellin Berthelot
. Abiogenic hypotheses were revived in the last half of the 20th century by Russian and Ukrainian scientists, who had little influence outside the Soviet Union because most of their research was published in their native languages. The theory was re-defined and made popular in the West by Thomas Gold
, who published all his research in English.
Although the abiogenic hypothesis was accepted by many geologists in the former Soviet Union, it allegedly fell out of favor because it never made any useful prediction for the discovery of oil deposits. Most geologists now consider the abiogenic formation of petroleum scientifically unsupported. The abiogenic origin of petroleum has also recently been reviewed in detail by Glasby, who raises a number of objections, including that there is no direct evidence to date of abiogenic petroleum (liquid crude oil and long-chain hydrocarbon compounds).
It has been recently discovered that thermophilic bacteria, in the sea bottom and in cooling magma, produce methane
and hydrocarbon gases, but studies indicate they are not produced in commercially significant quantities (i.e. in extracted hydrocarbon gases, the median abiogenic hydrocarbon content is 0.02%).
, much less that of biochemistry
, was established so the chemical nature of the petroleum was not known. Absent intellectual framework of organic and biological chemistry, abiologic theories were inevitable. In the early 19th century, Phlogiston theory
was the dominant model for explaining chemical phenomena. Furthermore, the formal study of paleontology
had only started in the early 19th century. It is within this scientifically primitive but changing environment that theories on the origin of petroleum originated.
Alexander von Humboldt
was the first to propose an inorganic abiogenic hypothesis for petroleum formation after he observed petroleum springs in the Bay of Cumaux (Cumaná
) on the northeast coast of Venezuela
. In 1804 he is quoted as saying, "petroleum is the product of a distillation from great depth and issues from the primitive rocks beneath which the forces of all volcanic action lie." Abraham Gottlob Werner
and the proponents of neptunism
in the 18th century believed basalt
ic sills
to be solidified oils or bitumen. While these notions have been proven unfounded, the basic idea that petroleum is associated with magmatism persisted. Other prominent proponents of what would become the abiogenic hypothesis included Mendeleev and Berthelot
.
Russian geologist Nikolai Alexandrovitch Kudryavtsev
proposed the modern abiotic hypothesis of petroleum in 1951. On the basis of his analysis of the Athabasca Oil Sands
in Alberta, Canada, he concluded that no "source rocks"
could form the enormous volume of hydrocarbons, and that therefore the most plausible explanation is abiotic deep petroleum. However, humic coals have since been proposed for the source rocks. Kudryavtsev's work was continued by Petr N. Kropotkin, Vladimir B. Porfir'ev, Emmanuil B. Chekaliuk
, Vladilen A. Krayushkin, Georgi E. Boyko
, Georgi I. Voitov, Grygori N. Dolenko
, Iona V. Greenberg, Nikolai S. Beskrovny, and Victor F. Linetsky.
Astronomer Thomas Gold
was the most prominent proponent of the abiogenic hypothesis in the West until his death in 2004. Currently, Jack Kenney of Gas Resources Corporation is a prominent proponent in the West.
and heavier hydrocarbons can be synthesized under conditions of the upper mantle. Research mostly related to astrobiology
and the deep microbial biosphere and serpentinite reactions, however, continue to provide insight into the contribution of abiogenic hydrocarbons into petroleum accumulations.
Similarly, research into the deep microbial hypothesis of hydrocarbon generation is advancing as part of the attempt to investigate the concept of panspermia and astrobiology
, specifically using deep microbial life as an analog for life on Mars
. Research applicable to deep microbial petroleum theories includes
A 2006 review article by Glasby presented arguments against the abiogenic origin of petroleum on a number of counts.
s, chiefly methane
and as elemental carbon, carbon dioxide and carbonates. The abiotic hypothesis is that the full suite of hydrocarbons found in petroleum can be generated in the mantle by abiogenic processes, and these hydrocarbons can migrate out of the mantle into the crust until they escape to the surface or are trapped by impermeable strata, forming petroleum reservoirs.
Abiogenic theories reject the supposition that certain molecules found within petroleum, known as biomarkers
, are indicative of the biological origin of petroleum. They contend that these molecules mostly come from microbes feeding on petroleum in its upward migration through the crust, that some of them are found in meteorites, which have presumably never contacted living material, and that some can be generated abiogenically by plausible reactions in petroleum.
The hypothesis is founded primarily upon:
. The theory was initially based on the isolation of molecules from petroleum that closely resemble known biomolecules (Figure).
Most petroleum geologists
prefer theories of oil formation
, which holds that oil originated in shallow seas
as vast quantities of marine plankton
or plant materials died and sank into the mud
. Under the resulting anaerobic conditions
organic compounds remained in a reduced
state where anaerobic bacteria
converted the lipid
s (fats, oils and waxes) into a waxy substance called kerogen
.
As the source rock
was buried deeper, overburden pressure
raised temperatures into the oil window, between 80 and 180 °C. Most of the organic compounds degraded into the straight-chain hydrocarbons
that comprise most of petroleum. This process is called the generation kitchen. Once crude oil formed, it became very fluid
and migrated upward through the rock strata
. This process is called oil expulsion. Eventually it was either trapped in an oil reservoir
or oil escaped to the surface
and was biodegraded
by soil bacteria.
Oil buried deeper entered the "gas window" of more than 160 °C and was converted into natural gas
by thermal cracking
. Thus, theory predicts that no oil will be found below a certain depth, only unassociated gas
. At greater depths, even natural gas would be pyrolyzed.
s, contain carbonaceous material. If a large amount of this material is still within the Earth, it could have been leaking upward for billions of years. The thermodynamic conditions within the mantle would allow many hydrocarbon molecules to be at equilibrium under high pressure and high temperature. Although molecules in these conditions may disassociate, resulting fragments would be reformed due to the pressure. An average equilibrium of various molecules would exist depending upon conditions and the carbon-hydrogen ratio of the material.
. Data from the western United States suggests that aquifer
s from near the surface may extend to depths of 10 to 20 km. Hydrogen gas can be created by water reacting with silicate
s, quartz
and feldspar
, in temperatures in the 25° to 270°C range. These minerals are common in crustal rocks such as granite
. Hydrogen may react with dissolved carbon compounds in water to form methane and higher carbon compounds.
One reaction not involving silicates which can create hydrogen is:
Ferrous oxide + Water → Magnetite + hydrogen
The above reaction operates best at low pressures. At pressures greater than 5 GPa almost no hydrogen is created.
scientist, Prof. Emmanuil B. Chekaliuk
in 1967. He proposed that petroleum could be formed at high temperatures and pressures from inorganic carbon in the form of carbon dioxide, hydrogen and/or methane.
This mechanism is supported by several lines of evidence which are accepted by modern scientific literature. This involves synthesis of oil within the crust via catalysis by chemically reductive rocks. A proposed mechanism for the formation of inorganic hydrocarbons is via natural analogs of the Fischer-Tropsch process
known as the serpentinite mechanism or the serpentinite process.
Serpentinites are ideal rocks to host this process as they are formed from peridotite
s and dunite
s, rocks which contain greater than 80% olivine
and usually a percentage of Fe-Ti spinel minerals. Most olivines also contain high nickel concentrations (up to several percent) and may also contain chromite or chromium as a contaminant in olivine, providing the needed transition metals.
However, serpentinite synthesis and spinel cracking reactions require hydrothermal alteration of pristine peridotite-dunite, which is a finite process intrinsically related to metamorphism, and further, requires significant addition of water. Serpentinite is unstable at mantle temperatures and is readily dehydrated to granulite
, amphibolite
, talc
–schist
and even eclogite
. This suggests that methanogenesis in the presence of serpentinites is restricted in space and time to mid-ocean ridges and upper levels of subduction zones. However, water has been found as deep as 12 km, so water-based reactions are dependent upon the local conditions. Oil being created by this process in intracratonic regions is limited by the materials and temperature.
of peridotite
, beginning with methanogenesis via hydrolysis of olivine into serpentine in the presence of carbon dioxide. Olivine, composed of Forsterite and Fayalite metamorphoses into serpentine, magnetite and silica by the following reactions, with silica from fayalite decomposition (reaction 1a) feeding into the forsterite reaction (1b).
Reaction 1a:
Fayalite + water → Magnetite + aqueous silica + Hydrogen
Reaction 1b:
Forsterite + aqueous silica → Serpentinite
When this reaction occurs in the presence of dissolved carbon dioxide (carbonic acid) at temperatures above 500 °C Reaction 2a takes place.
Reaction 2a:
Olivine + Water + Carbonic acid → Serpentine + Magnetite + Methane
or, in balanced form:
→ 
However, reaction 2(b) is just as likely, and supported by the presence of abundant talc-carbonate schists and magnesite stringer veins in many serpentinised peridotites;
Reaction 2b:
Olivine + Water + Carbonic acid → Serpentine + Magnetite + Magnesite + Silica
The upgrading of methane to higher n-alkane hydrocarbons is via dehydrogenation
of methane in the presence of catalyst transition metals (e.g. Fe, Ni). This can be termed spinel hydrolysis.
, chromite
and ilmenite
are Fe-spinel group minerals found in many rocks but rarely as a major component in non-ultramafic rocks. In these rocks, high concentrations of magmatic magnetite, chromite and ilmenite provide a reduced matrix which may allow abiotic cracking of methane to higher hydrocarbons during hydrothermal events.
Chemically reduced rocks are required to drive this reaction and high temperatures are required to allow methane to be polymerized to ethane. Note that reaction 1a, above, also creates magnetite.
Reaction 3:
Methane + Magnetite → Ethane + Hematite
Reaction 3 results in n-alkane hydrocarbons, including linear saturated hydrocarbons, alcohol
s, aldehyde
s, ketone
s, aromatics, and cyclic compounds.
Reaction 5:
Hydrogen + Calcium carbonate → Methane + Calcium oxide + Water
Note that CaO (lime) is not a mineral species found within natural rocks. Whilst this reaction is possible, it is not plausible.
deposits within the Earth's rocks can be explained purely according to the orthodox view of petroleum geology
. Thomas Gold
used the term the deep hot biosphere to describe the microbes which live underground.
This hypothesis is different from biogenic oil in that the role of deep-dwelling microbes is a biological source for oil which is not of a sedimentary origin and is not sourced from surface carbon. Deep microbial life is only a contaminant of primordial hydrocarbons. Parts of microbes yield molecules as biomarkers.
Deep biotic oil is considered to be formed as a byproduct of the life cycle of deep microbes.
Shallow biotic oil is considered to be formed as a byproduct of the life cycles of shallow microbes.
, in a 1999 book, cited the discovery of thermophile
bacteria in the Earth's crust as new support for the postulate that these bacteria could explain the existence of certain biomarker
s in extracted petroleum. A rebuttal of biogenic origins based on biomarkers has been offered by Kenney, et al. (2001).
is ubiquitous in crustal fluid and gas. Research continues to attempt to characterise crustal sources of methane as biogenic or abiogenic using carbon isotope fractionation of observed gases (Lollar & Sherwood 2006). There are few clear examples of abiogenic methane-ethane-butane, as the same processes favor enrichment of light isotopes in all chemical reactions, whether organic or inorganic. δ13C of methane overlaps that of inorganic carbonate and graphite in the crust, which are heavily depleted in 12C, and attain this by isotopic fractionation during metamorphic reactions.
One argument for abiogenic oil cites the high carbon depletion of methane as stemming from the observed carbon isotope depletion with depth in the crust. However, diamonds, which are definitively of mantle origin, are not as depleted as methane, which implies that methane carbon isotope fractionation is not controlled by mantle values.
Commercially extractable concentrations of helium
(greater than 0.3%) are present in natural gas from the Panhandle-Hugoton
fields in the USA, as well as from some Algerian and Russian gas fields.
Helium trapped within most petroleum occurrences, such as the occurrence in Texas, is of a distinctly crustal character with an Ra ratio of less than 0.0001 that of the atmosphere.
The Chimaera gas seep, near Antalya (SW Turkey), new and thorough molecular and isotopic analyses including methane (~87% v/v; D13C1 from -7.9 to -12.3 ‰; D13D1 from -119 to -124 ‰), light alkanes (C2+C3+C4+C5 = 0.5%; C6+: 0.07%; D13C2 from -24.2 to -26.5 ‰; D13C3 from -25.5 to -27 ‰), hydrogen (7.5 to 11 %), carbon dioxide (0.01-0.07%; D13CCO2: -15 ‰), helium (~80 ppmv; R/Ra: 0.41) and nitrogen (2-4.9%; D15N from -2 to -2.8 ‰) converge to indicate that the seep releases a mixture of organic thermogenic gas, related to mature Type III kerogen occurring in Paleozoic and Mesozoic organic rich sedimentary rocks, and abiogenic gas produced by low temperature serpentinization in the Tekirova ophiolitic unit. http://www3.interscience.wiley.com/journal/121537869/abstract
s, terpene
s, pristane
, phytane
, cholestane
, chlorin
s and porphyrin
s, which are large, chelating molecules in the same family as heme
and chlorophyll
. Materials which suggest certain biological processes include tetracyclic diterpane and oleanane.
The presence of these chemicals in crude oil is assumed to be as a result of the inclusion of biological material in the oil. This is predicated upon the theory that these chemicals are released by kerogen
during the production of hydrocarbon oils, as these are chemicals highly resistant to degradation and plausible chemical paths have been studied. Abiotic defenders state that biomarkers get into oil during its way up as it gets in touch with ancient fossils. However a more plausible explanation is that biomarkers are traces of biological molecules from bacteria (archaea) that feed on primordial hydrocarbons and die in that environment. For example, hopanoids are just parts of the bacterial cell wall present in oil as contaminant.
(Ni), vanadium
(V), lead
(Pb), arsenic
(As), cadmium
(Cd), mercury
(Hg) and others metals frequently occur in oils. Some heavy crude oils, such as Venezuelan heavy crude have up to 45% vanadium
pentoxide content in their ash, high enough that it is a commercial source for vanadium. Abiotic supporters argue that these metals are common in Earth's mantle, but relatively high contents of nickel, vanadium, lead and arsenic can be usually found in almost all marine sediments.
Analysis of 22 trace elements in oils correlate significantly better with chondrite
, serpentinized fertile mantle peridotite, and the primitive mantle than with oceanic or continental crust, and shows no correlation with seawater.
Olefins, the unsaturated hydrocarbons, would have been expected to predominate by far in any material that was derived in that way. He also wrote: "Petroleum ... [seems to be] a primordial hydrocarbon mixture into which bio-products have been added."
This has however been demonstrated later to be a misunderstanding by Robinson, related to the fact that only short duration experiments were available to him. Olefins are thermally very unstable (that is why natural petroleum normally does not contain such compounds) and in laboratory experiments that last more than a few hours, the olefins are no longer present.
The presence of low-oxygen and hydroxyl-poor hydrocarbons in natural living media is supported by the presence of natural waxes (n=30+), oils (n=20+) and lipids in both plant matter and animal matter, for instance fats in phytoplankton, zooplankton and so on. These oils and waxes, however, occur in quantities too small to significantly affect the overall hydrogen/carbon ratio of biological materials.
However, after the discovery of highly aliphatic biopolymers in algae, and that oil generating kerogen essentially represent concentrates of such materials, no theoretical problem exists anymore. Also, the millions of source rock samples that have been analyzed for petroleum yield by the petroleum industry have confirmed the large quantities of petroleum found in sedimentary basins.
The following observations have been commonly been used to argue for the abiogenic hypothesis, however all of these petroleum occurrences can also be fully explained by conventional petroleum formation theories.
was determined to have abiogenic hydrocarbon production. Proskurowski et al. wrote, "Radiocarbon evidence rules out seawater bicarbonate as the carbon source for FTT reactions, suggesting that a mantle-derived inorganic carbon source is leached from the host rocks. Our findings illustrate that the abiotic synthesis of hydrocarbons in nature may occur in the presence of ultramafic rocks, water, and moderate amounts of heat."
meteorite crater, Sweden, was proposed by Thomas Gold
as the most likely place to test the hypothesis because it was one of the few places in the world where the granite basement was cracked sufficiently (by meteorite impact) to allow oil to seep up from the mantle; furthermore it is infilled with a relatively thin veneer of sediment, which was sufficient to trap any abiogenic oil, but was modelled as not having been subjected to the heat and pressure conditions (known as the "oil window") normally required to create biogenic oil. However, some geochemists concluded by geochemical analysis that the oil in the seeps came from the organic-rich Ordivician Tretaspis shale, where it was heated by the meteorite impact.
The Gravberg-1 borehole penetrated 7,500 m, through the deepest rock in the Siljan Ring in which proponents had hoped to find hydrocarbon reservoirs. Some eight barrels of magnetite paste and hydrocarbon-bearing sludge were recovered from the well; Gold maintained that the hydrocarbons were chemically different from, and not derived from, those added to the borehole, but analyses showed that the hydrocarbons were derived from the diesel fuel-based drilling fluid used in the drilling. This well also sampled over 13000 feet (3,962.4 m) of methane-bearing inclusions.
A second borehole, Stenberg-1, was drilled a few miles away, finding similar results, This time no diesel fuel-based drilling fluid was found.
(Anadarko Basin
) in the south-central United States is the most important gas field with commercial helium content.
The Bạch Hổ oil field in Vietnam
has been proposed as an example of abiogenic oil because it is 4,000 m of fractured basement granite, at a depth of 5,000 m. However, others argue that it contains biogenic oil which leaked into the basement horst from conventional source rocks within the Cuu Long
basin.
A major component of mantle-derived carbon is indicated in commercial gas reservoirs in the Pannonian
and Vienna basin
s of Hungary and Austria.
Natural gas pools interpreted as being mantle-derived are the Shengli Field
and Songliao Basin, northeastern China.
The Chimaera gas seep, near Çıralı, Antalya (southwest Turkey), has been continuously active for millennia and it is known to be the source of the first Olympic fire in the Hellenistic period. On the basis of chemical composition and isotopic analysis, the Chimaera gas is said to be about half biogenic and half abiogenic gas, the largest emission of biogenic methane discovered; deep and pressurized gas accumulations necessary to sustain the gas flow for millennia, posited to be from an inorganic source, may be present. Local geology of Chimaera flames, at exact position of flames, reveals contact between serpentinized ophiolite and carbonate rocks. Fischer-Tropsch process can be suitable reaction to form hydrocarbons gases.
Key arguments against chemical reactions, such as the serpentinite mechanism, as being the major source of hydrocarbon deposits within the crust are;
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
that was proposed as an alternative to theory of biological petroleum origin. It was relatively popular in the past, but it went largely forgotten at the end of the 20th century after it failed to predict the location of new wells.
The abiogenic hypothesis argues that petroleum
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
was formed from deep carbon deposits, perhaps dating to the formation of the Earth
Formation and evolution of the Solar System
The formation and evolution of the Solar System is estimated to have begun 4.568 billion years ago with the gravitational collapse of a small part of a giant molecular cloud...
. Supporters of the abiogenic hypothesis suggest that a great deal more petroleum exists on Earth than commonly thought, and that petroleum may originate from carbon-bearing fluids that migrate upward from the mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....
. The presence of methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
on Saturn's moon Titan and in the atmospheres of Jupiter, Saturn, Uranus and Neptune is cited as evidence of the formation of hydrocarbons without biology.
The biogenic theory for petroleum was first proposed by Georg Agricola
Georg Agricola
Georgius Agricola was a German scholar and scientist. Known as "the father of mineralogy", he was born at Glauchau in Saxony. His real name was Georg Pawer; Agricola is the Latinised version of his name, Pawer meaning "farmer"...
in the 16th century and various abiogenic hypotheses were proposed in the 19th century, most notably by Alexander von Humboldt
Alexander von Humboldt
Friedrich Wilhelm Heinrich Alexander Freiherr von Humboldt was a German naturalist and explorer, and the younger brother of the Prussian minister, philosopher and linguist Wilhelm von Humboldt...
, the Russian chemist Dmitri Mendeleev
Dmitri Mendeleev
Dmitri Ivanovich Mendeleev , was a Russian chemist and inventor. He is credited as being the creator of the first version of the periodic table of elements...
and the French chemist Marcellin Berthelot
Marcellin Berthelot
Marcelin Pierre Eugène Berthelot was a French chemist and politician noted for the Thomsen-Berthelot principle of thermochemistry. He synthesized many organic compounds from inorganic substances and disproved the theory of vitalism. He is considered as one of the greatest chemists of all time.He...
. Abiogenic hypotheses were revived in the last half of the 20th century by Russian and Ukrainian scientists, who had little influence outside the Soviet Union because most of their research was published in their native languages. The theory was re-defined and made popular in the West by Thomas Gold
Thomas Gold
Thomas Gold was an Austrian-born astrophysicist, a professor of astronomy at Cornell University, a member of the U.S. National Academy of Sciences, and a Fellow of the Royal Society . Gold was one of three young Cambridge scientists who in the 1950s proposed the now mostly abandoned 'steady...
, who published all his research in English.
Although the abiogenic hypothesis was accepted by many geologists in the former Soviet Union, it allegedly fell out of favor because it never made any useful prediction for the discovery of oil deposits. Most geologists now consider the abiogenic formation of petroleum scientifically unsupported. The abiogenic origin of petroleum has also recently been reviewed in detail by Glasby, who raises a number of objections, including that there is no direct evidence to date of abiogenic petroleum (liquid crude oil and long-chain hydrocarbon compounds).
It has been recently discovered that thermophilic bacteria, in the sea bottom and in cooling magma, produce methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
and hydrocarbon gases, but studies indicate they are not produced in commercially significant quantities (i.e. in extracted hydrocarbon gases, the median abiogenic hydrocarbon content is 0.02%).
History of abiogenic hypothesis
The abiogenic theory for the origin of petroleum is usually traced to the early part of the 19th century. The hypothesis was developed well before the field of organic chemistryOrganic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
, much less that of biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
, was established so the chemical nature of the petroleum was not known. Absent intellectual framework of organic and biological chemistry, abiologic theories were inevitable. In the early 19th century, Phlogiston theory
Phlogiston theory
The phlogiston theory , first stated in 1667 by Johann Joachim Becher, is an obsolete scientific theory that postulated the existence of a fire-like element called "phlogiston", which was contained within combustible bodies and released during combustion...
was the dominant model for explaining chemical phenomena. Furthermore, the formal study of paleontology
History of paleontology
The history of paleontology traces the history of the effort to understand the history of life on Earth by studying the fossil record left behind by living organisms...
had only started in the early 19th century. It is within this scientifically primitive but changing environment that theories on the origin of petroleum originated.
Alexander von Humboldt
Alexander von Humboldt
Friedrich Wilhelm Heinrich Alexander Freiherr von Humboldt was a German naturalist and explorer, and the younger brother of the Prussian minister, philosopher and linguist Wilhelm von Humboldt...
was the first to propose an inorganic abiogenic hypothesis for petroleum formation after he observed petroleum springs in the Bay of Cumaux (Cumaná
Cumaná
Cumaná is the capital of Venezuela's Sucre State. It is located 402 km east of Caracas. It was the first settlement founded by Europeans in the mainland America, in 1501 by Franciscan friars, but due to successful attacks by the indigenous people, it had to be refounded several times...
) on the northeast coast of Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
. In 1804 he is quoted as saying, "petroleum is the product of a distillation from great depth and issues from the primitive rocks beneath which the forces of all volcanic action lie." Abraham Gottlob Werner
Abraham Gottlob Werner
Abraham Gottlob Werner , was a German geologist who set out an early theory about the stratification of the Earth's crust and coined the word Neptunism...
and the proponents of neptunism
Neptunism
Neptunism is a discredited and obsolete scientific theory of geology proposed by Abraham Gottlob Werner in the late 18th century that proposed rocks formed from the crystallisation of minerals in the early Earth's oceans....
in the 18th century believed basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic sills
Sill (geology)
In geology, a sill is a tabular sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive sheet...
to be solidified oils or bitumen. While these notions have been proven unfounded, the basic idea that petroleum is associated with magmatism persisted. Other prominent proponents of what would become the abiogenic hypothesis included Mendeleev and Berthelot
Marcellin Berthelot
Marcelin Pierre Eugène Berthelot was a French chemist and politician noted for the Thomsen-Berthelot principle of thermochemistry. He synthesized many organic compounds from inorganic substances and disproved the theory of vitalism. He is considered as one of the greatest chemists of all time.He...
.
Russian geologist Nikolai Alexandrovitch Kudryavtsev
Nikolai Kudryavtsev
Nikolai Alexandrovich Kudryavtsev was a Soviet Russian petroleum geologist. He is the founding father of modern abiogenic theory for origin of petroleum, which states that petroleum is formed from non-biological sources of hydrocarbons located deep in the Earth's crust and mantle.He graduated...
proposed the modern abiotic hypothesis of petroleum in 1951. On the basis of his analysis of the Athabasca Oil Sands
Athabasca Oil Sands
The Athabasca oil sands are large deposits of bitumen, or extremely heavy crude oil, located in northeastern Alberta, Canada - roughly centred on the boomtown of Fort McMurray...
in Alberta, Canada, he concluded that no "source rocks"
Source rock
In petroleum geology, source rock refers to rocks from which hydrocarbons have been generated or are capable of being generated. They form one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been deposited in a variety of environments including...
could form the enormous volume of hydrocarbons, and that therefore the most plausible explanation is abiotic deep petroleum. However, humic coals have since been proposed for the source rocks. Kudryavtsev's work was continued by Petr N. Kropotkin, Vladimir B. Porfir'ev, Emmanuil B. Chekaliuk
Emmanuil B. Chekaliuk
Emmanuïl Bogdanovych Chekaliuk was a Ukrainian petroleum engineer and statistical thermodynamicist. He first produced rigorous physical and mathematical evidences of petroleum thermodynamic stability at mantlean conditions...
, Vladilen A. Krayushkin, Georgi E. Boyko
Georgi E. Boyko
Georgi Yu. Boyko was a Ukrainian and Soviet petroleum geologist, one of the supporters and developers of the abiogenic petroleum origin hypothesis....
, Georgi I. Voitov, Grygori N. Dolenko
Grygori N. Dolenko
Grygori Nazarovych Dolenko was a Ukrainian petroleum geologist.Graduated from Kharkiv University . Worked for ChernomorNeft, KhadyzhenNeft, BuguruslanNeft, and UkrNefteRazvedka E&P companies and with Inst. of Geology and Geochemistry of Combustible Minerals of Nat'l Ac.Sci...
, Iona V. Greenberg, Nikolai S. Beskrovny, and Victor F. Linetsky.
Astronomer Thomas Gold
Thomas Gold
Thomas Gold was an Austrian-born astrophysicist, a professor of astronomy at Cornell University, a member of the U.S. National Academy of Sciences, and a Fellow of the Royal Society . Gold was one of three young Cambridge scientists who in the 1950s proposed the now mostly abandoned 'steady...
was the most prominent proponent of the abiogenic hypothesis in the West until his death in 2004. Currently, Jack Kenney of Gas Resources Corporation is a prominent proponent in the West.
State of current research
Little research is directed on establishing abiogenic petroleum or methane, although the Carnegie Institution for Science have found that ethaneEthane
Ethane is a chemical compound with chemical formula C2H6. It is the only two-carbon alkane that is an aliphatic hydrocarbon. At standard temperature and pressure, ethane is a colorless, odorless gas....
and heavier hydrocarbons can be synthesized under conditions of the upper mantle. Research mostly related to astrobiology
Astrobiology
Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe. This interdisciplinary field encompasses the search for habitable environments in our Solar System and habitable planets outside our Solar System, the search for evidence of prebiotic chemistry,...
and the deep microbial biosphere and serpentinite reactions, however, continue to provide insight into the contribution of abiogenic hydrocarbons into petroleum accumulations.
- rock porosity and migration pathways for abiogenic petroleum
- ocean floor hydrothermal ventHydrothermal ventA hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both...
s as in the Lost CityLost City (hydrothermal field)Lost City is a field of hydrothermal vents in the mid-Atlantic ocean that differ significantly from the black smoker vents found in the late 1970s. The vents were discovered in December 2000 during a National Science Foundation expedition to the mid-Atlantic. A second expedition mounted in 2003...
hydrothermal field; - Mud volcanoMud volcanoThe term mud volcano or mud dome are used to refer to formations created by geo-excreted liquids and gases, although there are several different processes which may cause such activity. Hot water mixes with mud and surface deposits. Mud volcanoes are associated with subduction zones and about 700...
es and the volatile contents of deep pelagic oozes and deep formation brines - mantle peridotitePeridotiteA peridotite is a dense, coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium, reflecting the high proportions of magnesium-rich olivine, with appreciable iron...
serpentinization reactions and other natural Fischer-Tropsch analogs - Primordial hydrocarbons in meteoriteMeteoriteA meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
s, cometCometA comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
s, asteroids and the solid bodies of the solar systemSolar SystemThe Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
- Primordial or ancient sources of hydrocarbons or carbon in Earth
- Primordial hydrocarbons formed from hydrolysis of metal carbides of the iron peak of cosmic elemental abundance (CrChromiumChromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
, FeIronIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, NiNickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
, VVanadiumVanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
, MnManganeseManganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
, CoCobaltCobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....
)
- Primordial hydrocarbons formed from hydrolysis of metal carbides of the iron peak of cosmic elemental abundance (Cr
- Primordial or ancient sources of hydrocarbons or carbon in Earth
- isotopic studies of groundwater reservoirs, sedimentary cements, formation gases and the composition of the noble gases and nitrogen in many oil fields
- the geochemistry of petroleum and the presence of trace metals related to Earth's mantle (NiNickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
, VVanadiumVanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
, CdCadmiumCadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
, AsArsenicArsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
, PbLeadLead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
, ZnZincZinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
, HgMercury (element)Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
and others)
Similarly, research into the deep microbial hypothesis of hydrocarbon generation is advancing as part of the attempt to investigate the concept of panspermia and astrobiology
Astrobiology
Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe. This interdisciplinary field encompasses the search for habitable environments in our Solar System and habitable planets outside our Solar System, the search for evidence of prebiotic chemistry,...
, specifically using deep microbial life as an analog for life on Mars
Life on Mars
Scientists have long speculated about the possibility of life on Mars owing to the planet's proximity and similarity to Earth. Fictional Martians have been a recurring feature of popular entertainment of the 20th and 21st centuries, but it remains an open question whether life currently exists on...
. Research applicable to deep microbial petroleum theories includes
- Research into how to sample deep reservoirs and rocks without contamination
- Sampling deep rocks and measuring chemistry and biological activity
- Possible energy sources and metabolic pathways which may be used in a deep biosphere
- Investigations into the reworking primordial hydrocarbons by bacteria and their effects on carbon isotope fractionation
A 2006 review article by Glasby presented arguments against the abiogenic origin of petroleum on a number of counts.
Foundations of the hypotheses
Within the mantle, carbon may exist as hydrocarbonHydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
s, chiefly methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
and as elemental carbon, carbon dioxide and carbonates. The abiotic hypothesis is that the full suite of hydrocarbons found in petroleum can be generated in the mantle by abiogenic processes, and these hydrocarbons can migrate out of the mantle into the crust until they escape to the surface or are trapped by impermeable strata, forming petroleum reservoirs.
Abiogenic theories reject the supposition that certain molecules found within petroleum, known as biomarkers
Biomarker (petroleum)
Biomarkers are any of a suite of complex organic compounds composed of carbon, hydrogen and other elements such as oxygen,nitrogen and sulfur, which are found in crude oils, bitumens and a petroleum source rock and eventually show simplification in molecular structure from the parent organic...
, are indicative of the biological origin of petroleum. They contend that these molecules mostly come from microbes feeding on petroleum in its upward migration through the crust, that some of them are found in meteorites, which have presumably never contacted living material, and that some can be generated abiogenically by plausible reactions in petroleum.
The hypothesis is founded primarily upon:
| Proponents | Item |
|---|---|
| Gold | The presence of methane on other planets, meteors, moons and comets |
| Gold, Kenney | Proposed mechanisms of abiotically chemically synthesizing hydrocarbons within the mantle |
| Kudryavtsev, Gold | Hydrocarbon-rich areas tend to be hydrocarbon-rich at many different levels |
| Kudryavtsev, Gold | Petroleum and methane deposits are found in large patterns related to deep-seated large-scale structural features of the crust rather than to the patchwork of sedimentary deposits |
| Gold | Interpretations of the chemical and isotopic composition of natural petroleum |
| Kudryavtsev, Gold | The presence of oil and methane within non-sedimentary rock Sedimentary rock Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution.... s upon the Earth |
| Gold | The existence of methane hydrate Methane clathrate Methane clathrate, also called methane hydrate, hydromethane, methane ice, "fire ice", natural gas hydrate or just gas hydrate, is a solid clathrate compound in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice... deposits |
| Gold | Perceived ambiguity in some assumptions and key evidence used in the orthodox biogenic petroleum theories |
| Gold | Bituminous coal Bituminous coal Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen. It is of higher quality than lignite coal but of poorer quality than Anthracite... creation is based upon deep hydrocarbon seep Seep A petroleum seep is a place where natural liquid or gaseous hydrocarbons escape to the earth's atmosphere and surface, normally under low pressure or flow. Seeps generally occur above either terrestrial or offshore petroleum accumulation structures... s |
| Gold | Surface carbon budget and oxygen levels stable over geologic time scales |
| Kudryavtsev, Gold | Biogenic theories do not explain some hydrocarbon deposit characteristics |
| Szatmari | The distribution of metals in crude oils fits better with upper serpentinized mantle, primitive mantle and chondrite patterns than oceanic and continental crust, and show no correlation with sea water |
| Gold | The association of hydrocarbons with helium Helium Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table... , a noble gas |
Conventional theories
According to generally accepted theory, petroleum is derived from ancient biomassBiomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
. The theory was initially based on the isolation of molecules from petroleum that closely resemble known biomolecules (Figure).
Petroleum geology
Petroleum geology refers to the specific set of geological disciplines that are applied to the search for hydrocarbons .-Sedimentary basin analysis:...
prefer theories of oil formation
Oil reservoir
A petroleum reservoir, or oil and gas reservoir, is a subsurface pool of hydrocarbons contained in porous or fractured rock formations. The naturally occurring hydrocarbons, such as crude oil or natural gas, are trapped by overlying rock formations with lower permeability...
, which holds that oil originated in shallow seas
Western Interior Seaway
The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves, Laramidia and Appalachia, during most of the mid- and late-Cretaceous Period...
as vast quantities of marine plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
or plant materials died and sank into the mud
Bay mud
Bay mud consists of thick deposits of soft, unconsolidated silty clay, which is saturated with water; these soil layers are situated at the bottom of certain estuaries, which are normally in temperate regions that have experienced cyclical glacial cycles...
. Under the resulting anaerobic conditions
Hypoxia (environmental)
Hypoxia, or oxygen depletion, is a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system...
organic compounds remained in a reduced
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
state where anaerobic bacteria
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...
converted the lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
s (fats, oils and waxes) into a waxy substance called kerogen
Kerogen
Kerogen is a mixture of organic chemical compounds that make up a portion of the organic matter in sedimentary rocks. It is insoluble in normal organic solvents because of the huge molecular weight of its component compounds. The soluble portion is known as bitumen. When heated to the right...
.
As the source rock
Source rock
In petroleum geology, source rock refers to rocks from which hydrocarbons have been generated or are capable of being generated. They form one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been deposited in a variety of environments including...
was buried deeper, overburden pressure
Overburden pressure
Overburden pressure, also called lithostatic pressure or vertical stress, is the pressure or stress imposed on a layer of soil or rock by the weight of overlying material.The overburden pressure at a depth z is given by...
raised temperatures into the oil window, between 80 and 180 °C. Most of the organic compounds degraded into the straight-chain hydrocarbons
Alkane
Alkanes are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds without any cycles...
that comprise most of petroleum. This process is called the generation kitchen. Once crude oil formed, it became very fluid
Fluid dynamics
In physics, fluid dynamics is a sub-discipline of fluid mechanics that deals with fluid flow—the natural science of fluids in motion. It has several subdisciplines itself, including aerodynamics and hydrodynamics...
and migrated upward through the rock strata
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
. This process is called oil expulsion. Eventually it was either trapped in an oil reservoir
Oil reservoir
A petroleum reservoir, or oil and gas reservoir, is a subsurface pool of hydrocarbons contained in porous or fractured rock formations. The naturally occurring hydrocarbons, such as crude oil or natural gas, are trapped by overlying rock formations with lower permeability...
or oil escaped to the surface
Seep
A petroleum seep is a place where natural liquid or gaseous hydrocarbons escape to the earth's atmosphere and surface, normally under low pressure or flow. Seeps generally occur above either terrestrial or offshore petroleum accumulation structures...
and was biodegraded
Biodegradation
Biodegradation or biotic degradation or biotic decomposition is the chemical dissolution of materials by bacteria or other biological means...
by soil bacteria.
Oil buried deeper entered the "gas window" of more than 160 °C and was converted into natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
by thermal cracking
Cracking (chemistry)
In petroleum geology and chemistry, cracking is the process whereby complex organic molecules such as kerogens or heavy hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. The rate of cracking and the end products...
. Thus, theory predicts that no oil will be found below a certain depth, only unassociated gas
Natural gas field
Oil and natural gas are produced by the same geological process according fossil fuel suggestion: anaerobic decay of organic matter deep under the Earth's surface. As a consequence, oil and natural gas are often found together...
. At greater depths, even natural gas would be pyrolyzed.
Primordial deposits
Thomas Gold's work was focused on hydrocarbon deposits of primordial origin. Meteorites are believed to represent the major composition of material from which the Earth was formed. Some meteorites, such as carbonaceous chondriteCarbonaceous chondrite
Carbonaceous chondrites or C chondrites are a class of chondritic meteorites comprising at least 7 known groups and many ungrouped meteorites. They include some of the most primitive known meteorites...
s, contain carbonaceous material. If a large amount of this material is still within the Earth, it could have been leaking upward for billions of years. The thermodynamic conditions within the mantle would allow many hydrocarbon molecules to be at equilibrium under high pressure and high temperature. Although molecules in these conditions may disassociate, resulting fragments would be reformed due to the pressure. An average equilibrium of various molecules would exist depending upon conditions and the carbon-hydrogen ratio of the material.
Creation within the mantle
Russian researchers concluded that hydrocarbon mixes would be created within the mantle. Experiments under high temperatures and pressures produced many hydrocarbons, including n-alkanes through C10H22, from iron oxide, calcium carbonate, and water. Because such materials are in the mantle and in subducted crust, there is no requirement that all hydrocarbons be produced from primordial deposits.Hydrogen generation
Hydrogen gas and water have been found more than 6 kilometers deep in the upper crust, including in the Siljan Ring boreholes and the Kola Superdeep BoreholeKola Superdeep Borehole
The Kola Superdeep Borehole is the result of a scientific drilling project of the Soviet Union in Kola Peninsula. The project attempted to drill as deep as possible into the Earth's crust. Drilling began on 24 May 1970 using the Uralmash-4E, and later the Uralmash-15000 series drilling rig. A...
. Data from the western United States suggests that aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
s from near the surface may extend to depths of 10 to 20 km. Hydrogen gas can be created by water reacting with silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
s, quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
and feldspar
Feldspar
Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....
, in temperatures in the 25° to 270°C range. These minerals are common in crustal rocks such as granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
. Hydrogen may react with dissolved carbon compounds in water to form methane and higher carbon compounds.
One reaction not involving silicates which can create hydrogen is:
Ferrous oxide + Water → Magnetite + hydrogen
The above reaction operates best at low pressures. At pressures greater than 5 GPa almost no hydrogen is created.
Serpentinite mechanism
One proposed mechanism by which abiogenic petroleum is formed was first proposed by the UkrainianUkrainians
Ukrainians are an East Slavic ethnic group native to Ukraine, which is the sixth-largest nation in Europe. The Constitution of Ukraine applies the term 'Ukrainians' to all its citizens...
scientist, Prof. Emmanuil B. Chekaliuk
Emmanuil B. Chekaliuk
Emmanuïl Bogdanovych Chekaliuk was a Ukrainian petroleum engineer and statistical thermodynamicist. He first produced rigorous physical and mathematical evidences of petroleum thermodynamic stability at mantlean conditions...
in 1967. He proposed that petroleum could be formed at high temperatures and pressures from inorganic carbon in the form of carbon dioxide, hydrogen and/or methane.
This mechanism is supported by several lines of evidence which are accepted by modern scientific literature. This involves synthesis of oil within the crust via catalysis by chemically reductive rocks. A proposed mechanism for the formation of inorganic hydrocarbons is via natural analogs of the Fischer-Tropsch process
Fischer-Tropsch process
The Fischer–Tropsch process is a set of chemical reactions that convert a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. The process, a key component of gas to liquids technology, produces a petroleum substitute, typically from coal, natural gas, or biomass for use as synthetic...
known as the serpentinite mechanism or the serpentinite process.
Serpentinites are ideal rocks to host this process as they are formed from peridotite
Peridotite
A peridotite is a dense, coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium, reflecting the high proportions of magnesium-rich olivine, with appreciable iron...
s and dunite
Dunite
Dunite is an igneous, plutonic rock, of ultramafic composition, with coarse-grained or phaneritic texture. The mineral assemblage is greater than 90% olivine, with minor amounts of other minerals such as pyroxene, chromite and pyrope. Dunite is the olivine-rich end-member of the peridotite group...
s, rocks which contain greater than 80% olivine
Olivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....
and usually a percentage of Fe-Ti spinel minerals. Most olivines also contain high nickel concentrations (up to several percent) and may also contain chromite or chromium as a contaminant in olivine, providing the needed transition metals.
However, serpentinite synthesis and spinel cracking reactions require hydrothermal alteration of pristine peridotite-dunite, which is a finite process intrinsically related to metamorphism, and further, requires significant addition of water. Serpentinite is unstable at mantle temperatures and is readily dehydrated to granulite
Granulite
Granulites are medium to coarse–grained metamorphic rocks that have experienced high temperature metamorphism, composed mainly of feldspars sometimes associated with quartz and anhydrous ferromagnesian minerals, with granoblastic texture and gneissose to massive structure...
, amphibolite
Amphibolite
Amphibolite is the name given to a rock consisting mainly of hornblende amphibole, the use of the term being restricted, however, to metamorphic rocks. The modern terminology for a holocrystalline plutonic igneous rocks composed primarily of hornblende amphibole is a hornblendite, which are...
, talc
Talc
Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg34 or Mg3Si4O102. In loose form, it is the widely-used substance known as talcum powder. It occurs as foliated to fibrous masses, its crystals being so rare as to be almost unknown...
–schist
Schist
The schists constitute a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is...
and even eclogite
Eclogite
Eclogite is a mafic metamorphic rock. Eclogite is of special interest for at least two reasons. First, it forms at pressures greater than those typical of the crust of the Earth...
. This suggests that methanogenesis in the presence of serpentinites is restricted in space and time to mid-ocean ridges and upper levels of subduction zones. However, water has been found as deep as 12 km, so water-based reactions are dependent upon the local conditions. Oil being created by this process in intracratonic regions is limited by the materials and temperature.
Serpentinite synthesis
A chemical basis for the abiotic petroleum process is the serpentinizationSerpentinite
Serpentinite is a rock composed of one or more serpentine group minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle...
of peridotite
Peridotite
A peridotite is a dense, coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium, reflecting the high proportions of magnesium-rich olivine, with appreciable iron...
, beginning with methanogenesis via hydrolysis of olivine into serpentine in the presence of carbon dioxide. Olivine, composed of Forsterite and Fayalite metamorphoses into serpentine, magnetite and silica by the following reactions, with silica from fayalite decomposition (reaction 1a) feeding into the forsterite reaction (1b).
Reaction 1a:
Fayalite + water → Magnetite + aqueous silica + Hydrogen
Reaction 1b:
Forsterite + aqueous silica → Serpentinite
When this reaction occurs in the presence of dissolved carbon dioxide (carbonic acid) at temperatures above 500 °C Reaction 2a takes place.
Reaction 2a:
Olivine + Water + Carbonic acid → Serpentine + Magnetite + Methane
or, in balanced form:
→ However, reaction 2(b) is just as likely, and supported by the presence of abundant talc-carbonate schists and magnesite stringer veins in many serpentinised peridotites;
Reaction 2b:
Olivine + Water + Carbonic acid → Serpentine + Magnetite + Magnesite + Silica
The upgrading of methane to higher n-alkane hydrocarbons is via dehydrogenation
Dehydrogenation
Dehydrogenation is a chemical reaction that involves the elimination of hydrogen . It is the reverse process of hydrogenation. Dehydrogenation reactions may be either large scale industrial processes or smaller scale laboratory procedures....
of methane in the presence of catalyst transition metals (e.g. Fe, Ni). This can be termed spinel hydrolysis.
Spinel polymerization mechanism
MagnetiteMagnetite
Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...
, chromite
Chromite
Chromite is an iron chromium oxide: FeCr2O4. It is an oxide mineral belonging to the spinel group. Magnesium can substitute for iron in variable amounts as it forms a solid solution with magnesiochromite ; substitution of aluminium occurs leading to hercynite .-Occurrence:Chromite is found in...
and ilmenite
Ilmenite
Ilmenite is a weakly magnetic titanium-iron oxide mineral which is iron-black or steel-gray. It is a crystalline iron titanium oxide . It crystallizes in the trigonal system, and it has the same crystal structure as corundum and hematite....
are Fe-spinel group minerals found in many rocks but rarely as a major component in non-ultramafic rocks. In these rocks, high concentrations of magmatic magnetite, chromite and ilmenite provide a reduced matrix which may allow abiotic cracking of methane to higher hydrocarbons during hydrothermal events.
Chemically reduced rocks are required to drive this reaction and high temperatures are required to allow methane to be polymerized to ethane. Note that reaction 1a, above, also creates magnetite.
Reaction 3:
Methane + Magnetite → Ethane + Hematite
Reaction 3 results in n-alkane hydrocarbons, including linear saturated hydrocarbons, alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
s, aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
s, ketone
Ketone
In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
s, aromatics, and cyclic compounds.
Carbonate decomposition
Calcium carbonate may decompose at around 500 °C through the following reaction:Reaction 5:
Hydrogen + Calcium carbonate → Methane + Calcium oxide + Water
Note that CaO (lime) is not a mineral species found within natural rocks. Whilst this reaction is possible, it is not plausible.
Evidence of abiogenic mechanisms
- Calculations by J.F. Kenney using scaled particle theory for a simplified perturbed hard-chain, (a statistical mechanical model) predict that methane compressed to 30 or 40 kbar at 1000 °C (conditions in the mantle) is relatively unstable in relation to higher hydrocarbons. However, these calculations do not include methane pyrolisis yielding amorphous carbon and hydrogen, which is recognized as the prevalent reaction at high temperatures.
- Experiments in diamond anvil high pressure cells have resulted in partial conversion of methane and inorganic carbonates into light hydrocarbons.
Biotic (microbial) hydrocarbons
The "deep biotic petroleum hypothesis", similar to the abiogenic petroleum origin hypothesis, holds that not all petroleumPetroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
deposits within the Earth's rocks can be explained purely according to the orthodox view of petroleum geology
Petroleum geology
Petroleum geology refers to the specific set of geological disciplines that are applied to the search for hydrocarbons .-Sedimentary basin analysis:...
. Thomas Gold
Thomas Gold
Thomas Gold was an Austrian-born astrophysicist, a professor of astronomy at Cornell University, a member of the U.S. National Academy of Sciences, and a Fellow of the Royal Society . Gold was one of three young Cambridge scientists who in the 1950s proposed the now mostly abandoned 'steady...
used the term the deep hot biosphere to describe the microbes which live underground.
This hypothesis is different from biogenic oil in that the role of deep-dwelling microbes is a biological source for oil which is not of a sedimentary origin and is not sourced from surface carbon. Deep microbial life is only a contaminant of primordial hydrocarbons. Parts of microbes yield molecules as biomarkers.
Deep biotic oil is considered to be formed as a byproduct of the life cycle of deep microbes.
Shallow biotic oil is considered to be formed as a byproduct of the life cycles of shallow microbes.
Microbial biomarkers
Thomas GoldThomas Gold
Thomas Gold was an Austrian-born astrophysicist, a professor of astronomy at Cornell University, a member of the U.S. National Academy of Sciences, and a Fellow of the Royal Society . Gold was one of three young Cambridge scientists who in the 1950s proposed the now mostly abandoned 'steady...
, in a 1999 book, cited the discovery of thermophile
Thermophile
A thermophile is an organism — a type of extremophile — that thrives at relatively high temperatures, between 45 and 122 °C . Many thermophiles are archaea...
bacteria in the Earth's crust as new support for the postulate that these bacteria could explain the existence of certain biomarker
Biomarker (petroleum)
Biomarkers are any of a suite of complex organic compounds composed of carbon, hydrogen and other elements such as oxygen,nitrogen and sulfur, which are found in crude oils, bitumens and a petroleum source rock and eventually show simplification in molecular structure from the parent organic...
s in extracted petroleum. A rebuttal of biogenic origins based on biomarkers has been offered by Kenney, et al. (2001).
Isotopic evidence
MethaneMethane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
is ubiquitous in crustal fluid and gas. Research continues to attempt to characterise crustal sources of methane as biogenic or abiogenic using carbon isotope fractionation of observed gases (Lollar & Sherwood 2006). There are few clear examples of abiogenic methane-ethane-butane, as the same processes favor enrichment of light isotopes in all chemical reactions, whether organic or inorganic. δ13C of methane overlaps that of inorganic carbonate and graphite in the crust, which are heavily depleted in 12C, and attain this by isotopic fractionation during metamorphic reactions.
One argument for abiogenic oil cites the high carbon depletion of methane as stemming from the observed carbon isotope depletion with depth in the crust. However, diamonds, which are definitively of mantle origin, are not as depleted as methane, which implies that methane carbon isotope fractionation is not controlled by mantle values.
Commercially extractable concentrations of helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
(greater than 0.3%) are present in natural gas from the Panhandle-Hugoton
Hugoton Natural Gas Area
Hugoton Natural Gas Area is a combination of large natural gas fields in the U.S. state of Kansas, the largest of which is the Hugoton Field. Its name is derived from the town of Hugoton, Kansas, near which the Hugoton Field was first discovered.-History:...
fields in the USA, as well as from some Algerian and Russian gas fields.
Helium trapped within most petroleum occurrences, such as the occurrence in Texas, is of a distinctly crustal character with an Ra ratio of less than 0.0001 that of the atmosphere.
The Chimaera gas seep, near Antalya (SW Turkey), new and thorough molecular and isotopic analyses including methane (~87% v/v; D13C1 from -7.9 to -12.3 ‰; D13D1 from -119 to -124 ‰), light alkanes (C2+C3+C4+C5 = 0.5%; C6+: 0.07%; D13C2 from -24.2 to -26.5 ‰; D13C3 from -25.5 to -27 ‰), hydrogen (7.5 to 11 %), carbon dioxide (0.01-0.07%; D13CCO2: -15 ‰), helium (~80 ppmv; R/Ra: 0.41) and nitrogen (2-4.9%; D15N from -2 to -2.8 ‰) converge to indicate that the seep releases a mixture of organic thermogenic gas, related to mature Type III kerogen occurring in Paleozoic and Mesozoic organic rich sedimentary rocks, and abiogenic gas produced by low temperature serpentinization in the Tekirova ophiolitic unit. http://www3.interscience.wiley.com/journal/121537869/abstract
Biomarker chemicals
Certain chemicals found in naturally occurring petroleum contain chemical and structural similarities to compounds found within many living organisms. These include terpenoidTerpenoid
The terpenoids , sometimes called isoprenoids, are a large and diverse class of naturally occurring organic chemicals similar to terpenes, derived from five-carbon isoprene units assembled and modified in thousands of ways. Most are multicyclic structures that differ from one another not only in...
s, terpene
Terpene
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...
s, pristane
Pristane
Pristane is a natural saturated terpenoid alkane obtained primarily from shark liver oil, from which its name is derived . It is also found in mineral oil and some foods...
, phytane
Phytane
Phytane is a diterpenoid alkane. In contrast to pristane, which is formed from the decarboxylation of phytol, it has one extra carbon.Phytanyl is the corresponding substituent. Phytanyl groups are frequently found in phospholipids in membranes of thermophilic Archaea...
, cholestane
Cholestane
Cholestane is a saturated 27-carbon steroid precursor which serves as the basis for many organic molecules.- Derivatives of cholestane :Derivatives are classified in two families:* Sterols * Cholestenes...
, chlorin
Chlorin
In organic chemistry, a chlorin is a large heterocyclic aromatic ring consisting, at the core, of three pyrroles and one pyrroline coupled through four methine linkages...
s and porphyrin
Porphyrin
Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells; heme is a cofactor of the protein hemoglobin. Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at...
s, which are large, chelating molecules in the same family as heme
Heme
A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as their prosthetic group; these are...
and chlorophyll
Chlorophyll
Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...
. Materials which suggest certain biological processes include tetracyclic diterpane and oleanane.
The presence of these chemicals in crude oil is assumed to be as a result of the inclusion of biological material in the oil. This is predicated upon the theory that these chemicals are released by kerogen
Kerogen
Kerogen is a mixture of organic chemical compounds that make up a portion of the organic matter in sedimentary rocks. It is insoluble in normal organic solvents because of the huge molecular weight of its component compounds. The soluble portion is known as bitumen. When heated to the right...
during the production of hydrocarbon oils, as these are chemicals highly resistant to degradation and plausible chemical paths have been studied. Abiotic defenders state that biomarkers get into oil during its way up as it gets in touch with ancient fossils. However a more plausible explanation is that biomarkers are traces of biological molecules from bacteria (archaea) that feed on primordial hydrocarbons and die in that environment. For example, hopanoids are just parts of the bacterial cell wall present in oil as contaminant.
Trace metals
NickelNickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
(Ni), vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
(V), lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
(Pb), arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
(As), cadmium
Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
(Cd), mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
(Hg) and others metals frequently occur in oils. Some heavy crude oils, such as Venezuelan heavy crude have up to 45% vanadium
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
pentoxide content in their ash, high enough that it is a commercial source for vanadium. Abiotic supporters argue that these metals are common in Earth's mantle, but relatively high contents of nickel, vanadium, lead and arsenic can be usually found in almost all marine sediments.
Analysis of 22 trace elements in oils correlate significantly better with chondrite
Chondrite
Chondrites are stony meteorites that have not been modified due to melting or differentiation of the parent body. They formed when various types of dust and small grains that were present in the early solar system accreted to form primitive asteroids...
, serpentinized fertile mantle peridotite, and the primitive mantle than with oceanic or continental crust, and shows no correlation with seawater.
Reduced carbon
Sir Robert Robinson studied the chemical makeup of natural petroleum oils in great detail, and concluded that they were mostly far too hydrogen-rich to be a likely product of the decay of plant debris, assuming a dual origin for Earth hydrocarbons. However, several processes which generate hydrogen could supply kerogen hydrogenation which is compatible with conventional petroleum generation theories.Olefins, the unsaturated hydrocarbons, would have been expected to predominate by far in any material that was derived in that way. He also wrote: "Petroleum ... [seems to be] a primordial hydrocarbon mixture into which bio-products have been added."
This has however been demonstrated later to be a misunderstanding by Robinson, related to the fact that only short duration experiments were available to him. Olefins are thermally very unstable (that is why natural petroleum normally does not contain such compounds) and in laboratory experiments that last more than a few hours, the olefins are no longer present.
The presence of low-oxygen and hydroxyl-poor hydrocarbons in natural living media is supported by the presence of natural waxes (n=30+), oils (n=20+) and lipids in both plant matter and animal matter, for instance fats in phytoplankton, zooplankton and so on. These oils and waxes, however, occur in quantities too small to significantly affect the overall hydrogen/carbon ratio of biological materials.
However, after the discovery of highly aliphatic biopolymers in algae, and that oil generating kerogen essentially represent concentrates of such materials, no theoretical problem exists anymore. Also, the millions of source rock samples that have been analyzed for petroleum yield by the petroleum industry have confirmed the large quantities of petroleum found in sedimentary basins.
Field observations
Field observations sometimes cited as commercial occurrence of abiotic petroleum, but disputed by critics, include the Siljan Ring, offshore Vietnam, Eugene Island block 330 oil field, and the Dnieper-Donets Basin. The Russian-Ukrainian school saw evidence of their theory in the fact that some oil reservoirs exist in non-sedimentary rocks such as granite, metamorphic or porous volcanic rocks. However, critics note that non-sedimentary rocks served as reservoirs for oil expelled from nearby sedimentary source rock through common migration or re-migration mechanisms.The following observations have been commonly been used to argue for the abiogenic hypothesis, however all of these petroleum occurrences can also be fully explained by conventional petroleum formation theories.
Lost City Hydrothermal Vent Field
The Lost City Hydrothermal Vent FieldLost City (hydrothermal field)
Lost City is a field of hydrothermal vents in the mid-Atlantic ocean that differ significantly from the black smoker vents found in the late 1970s. The vents were discovered in December 2000 during a National Science Foundation expedition to the mid-Atlantic. A second expedition mounted in 2003...
was determined to have abiogenic hydrocarbon production. Proskurowski et al. wrote, "Radiocarbon evidence rules out seawater bicarbonate as the carbon source for FTT reactions, suggesting that a mantle-derived inorganic carbon source is leached from the host rocks. Our findings illustrate that the abiotic synthesis of hydrocarbons in nature may occur in the presence of ultramafic rocks, water, and moderate amounts of heat."
Siljan Ring, Sweden
The Siljan RingSiljan (lake)
Siljan, in Dalarna in central Sweden, is Sweden's sixth largest lake. The cumulative area of Siljan and the adjacent, smaller lakes Orsasjön and Insjön is . Siljan reaches a maximum depth of , and its surface is situated above sea level...
meteorite crater, Sweden, was proposed by Thomas Gold
Thomas Gold
Thomas Gold was an Austrian-born astrophysicist, a professor of astronomy at Cornell University, a member of the U.S. National Academy of Sciences, and a Fellow of the Royal Society . Gold was one of three young Cambridge scientists who in the 1950s proposed the now mostly abandoned 'steady...
as the most likely place to test the hypothesis because it was one of the few places in the world where the granite basement was cracked sufficiently (by meteorite impact) to allow oil to seep up from the mantle; furthermore it is infilled with a relatively thin veneer of sediment, which was sufficient to trap any abiogenic oil, but was modelled as not having been subjected to the heat and pressure conditions (known as the "oil window") normally required to create biogenic oil. However, some geochemists concluded by geochemical analysis that the oil in the seeps came from the organic-rich Ordivician Tretaspis shale, where it was heated by the meteorite impact.
The Gravberg-1 borehole penetrated 7,500 m, through the deepest rock in the Siljan Ring in which proponents had hoped to find hydrocarbon reservoirs. Some eight barrels of magnetite paste and hydrocarbon-bearing sludge were recovered from the well; Gold maintained that the hydrocarbons were chemically different from, and not derived from, those added to the borehole, but analyses showed that the hydrocarbons were derived from the diesel fuel-based drilling fluid used in the drilling. This well also sampled over 13000 feet (3,962.4 m) of methane-bearing inclusions.
A second borehole, Stenberg-1, was drilled a few miles away, finding similar results, This time no diesel fuel-based drilling fluid was found.
Bacterial mats
Direct observation of bacterial mats and fracture-fill carbonate and humin of bacterial origin in deep boreholes in Iran, Australia, Sweden and Canada are also taken as evidence for the abiogenic origin of petroleumExample proposed abiogenic methane deposits
Panhandle-Hugoton fieldHugoton Natural Gas Area
Hugoton Natural Gas Area is a combination of large natural gas fields in the U.S. state of Kansas, the largest of which is the Hugoton Field. Its name is derived from the town of Hugoton, Kansas, near which the Hugoton Field was first discovered.-History:...
(Anadarko Basin
Anadarko Basin
The Anadarko Basin is a geologic depositional and structural basin centered in the western part of the state of Oklahoma and the Texas Panhandle, and extending into western Kansas and southeast Colorado.-Geology:...
) in the south-central United States is the most important gas field with commercial helium content.
The Bạch Hổ oil field in Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
has been proposed as an example of abiogenic oil because it is 4,000 m of fractured basement granite, at a depth of 5,000 m. However, others argue that it contains biogenic oil which leaked into the basement horst from conventional source rocks within the Cuu Long
Cuu Long
Cửu Long was a province in the Mekong Delta region of southern Vietnam. It was created in 1976 from the merger of Vinh Long Province and Vinh Binh Province...
basin.
A major component of mantle-derived carbon is indicated in commercial gas reservoirs in the Pannonian
Pannonian Basin
The Pannonian Basin or Carpathian Basin is a large basin in East-Central Europe.The geomorphological term Pannonian Plain is more widely used for roughly the same region though with a somewhat different sense - meaning only the lowlands, the plain that remained when the Pliocene Pannonian Sea dried...
and Vienna basin
Vienna Basin
The Vienna Basin is a sedimentary basin between the Alps and the Carpathian Mountains...
s of Hungary and Austria.
Natural gas pools interpreted as being mantle-derived are the Shengli Field
Shengli Field
The Shengli Oil Field is the second-largest oil field in the People's Republic of China, with daily production of approximately .It is located in the Yellow River delta, in the north of Shandong province bordering Bohai Sea...
and Songliao Basin, northeastern China.
The Chimaera gas seep, near Çıralı, Antalya (southwest Turkey), has been continuously active for millennia and it is known to be the source of the first Olympic fire in the Hellenistic period. On the basis of chemical composition and isotopic analysis, the Chimaera gas is said to be about half biogenic and half abiogenic gas, the largest emission of biogenic methane discovered; deep and pressurized gas accumulations necessary to sustain the gas flow for millennia, posited to be from an inorganic source, may be present. Local geology of Chimaera flames, at exact position of flames, reveals contact between serpentinized ophiolite and carbonate rocks. Fischer-Tropsch process can be suitable reaction to form hydrocarbons gases.
The geological argument for abiogenic oil
Given the known occurrence of methane and the probable catalysis of methane into higher atomic weight hydrocarbon molecules, the abiogenic hypothesis considers the following to be key observations in support;- The serpentinite synthesis, graphite synthesis and spinel catalysation models prove the process is viable
- The likelihood that abiogenic oil seeping up from the mantle is trapped beneath sediments which effectively seal mantle-tapping faults
- Mass-balance calculations for supergiant oilfields which argue that the calculated source rock could not have supplied the reservoir with the known accumulation of oil, implying deep recharge (Kudryavtsev, 1951)
- The presence of hydrocarbons encapsulated in diamonds
Incidental evidence
The proponents of abiogenic oil use several arguments which draw on a variety of natural phenomena in order to support the hypothesis- The modelling of some researchers which shows the Earth was accreted at relatively low temperature, thereby perhaps preserving primordial carbon deposits within the mantle, to drive abiogenic hydrocarbon production
- The presence of methane within the gases and fluids of mid-ocean ridge spreading centre hydrothermal fields
The geological argument against
- The lack of available pore space within rocks as depth increases
- This is contradicted by numerous studies which have documented the existence of hydrologic systems operating over a range of scales and at all depths in the continental crust.
- The lack of any hydrocarbon within the crystalline shield areas of the major cratonCratonA craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
s, especially around key deep seated structures which are predicted to host oil by the abiogenic hypothesis. See Siljan Lake. - Limited evidence that major serpentinite belts underlie continental sedimentary basins which host oil
- Lack of conclusive proof that carbon isotope fractionation observed in crustal methane sources is entirely of abiogenic origin (Lollar et al. 2006)
- Mass balance problems of supplying enough carbon dioxide to serpentinite within the metamorphic event before the peridotite is fully reacted to serpentinite
- Drilling of the Siljan Ring failed to find commercial quantities of oil, thus providing a counter example to Kudryavtsev's Rule and failing to locate the predicted abiogenic oil.
- Helium in the Siljan Gravberg-1 well was depleted in 3HeHelium-3Helium-3 is a light, non-radioactive isotope of helium with two protons and one neutron. It is rare on Earth, and is sought for use in nuclear fusion research...
and not consistent with a mantle origin- The Gravberg-1 well only produced 84 barrels (13,354.9 l) of oil, which later was shown to derive from organic additives, lubricants and mud used in the drilling process.
- The distribution of sedimentary basins is caused by plate tectonics, with sedimentary basins forming on either side of a volcanic arcVolcanic arcA volcanic arc is a chain of volcanoes positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic island arc. Generally they result from the subduction of an oceanic tectonic plate under another tectonic plate, and often parallel an oceanic trench...
, which explains the distribution of oil within these sedimentary basins - Kudryavtsev's Rule has been explained for oil and gas (not coal): Gas deposits which are below oil deposits can be created from that oil or its source rocks. Because natural gas is less dense than oil, as kerogen and hydrocarbons are generating gas the gas fills the top of the available space. Oil is forced down, and can reach the spill point where oil leaks around the edge(s) of the formation and flows upward. If the original formation becomes completely filled with gas then all the oil will have leaked above the original location.
- Ubiquitous presence of diamondoidDiamondoidA diamondoid, in the context of building materials for nanotechnology components, most generally refers to structures that resemble diamond in a broad sense: namely, strong, stiff structures containing dense, 3-D networks of covalent bonds, formed chiefly from first and second row atoms with a...
s in natural hydrocarbons such as oil, gas and condensates are composed of carbon from biological sources, unlike the carbon found in normal diamonds.
Arguments against the incidental evidence
- Gas ruptures during earthquakes are more likely to be sourced from biogenic methane generated in unconsolidated sediment from existing organic matter, released by earthquake liquefaction of the reservoir during tremors
- The presence of methane hydrate is arguably produced by bacterial action upon organic detritus falling from the littoralLittoralThe littoral zone is that part of a sea, lake or river that is close to the shore. In coastal environments the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged. It always includes this intertidal zone and is often used to...
zone and trapped in the depth due to pressure and temperature - The likelihood of vast concentrations of methane in the mantle is very slim, given mantle xenoliths have negligible methane in their fluid inclusions; conventional plate tectonics explains deep focus quakes better, and the extreme confining pressures invalidate the hypothesis of gas pockets causing quakes
- Further evidence is the presence of diamond within kimberliteKimberliteKimberlite is a type of potassic volcanic rock best known for sometimes containing diamonds. It is named after the town of Kimberley in South Africa, where the discovery of an diamond in 1871 spawned a diamond rush, eventually creating the Big Hole....
s and lamproiteLamproiteLamproites are ultrapotassic mantle-derived volcanic and subvolcanic rocks. They have low CaO, Al2O3, Na2O, high K2O/Al2O3, a relatively high MgO content and extreme enrichment in incompatible elements....
s which sample the mantle depths proposed as being the source region of mantle methane (by Gold et al.).
See also
- Eugene Island block 330 oil field
- Fischer-Tropsch processFischer-Tropsch processThe Fischer–Tropsch process is a set of chemical reactions that convert a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. The process, a key component of gas to liquids technology, produces a petroleum substitute, typically from coal, natural gas, or biomass for use as synthetic...
- Fossil fuelFossil fuelFossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years...
- Nikolai Alexandrovitch KudryavtsevNikolai KudryavtsevNikolai Alexandrovich Kudryavtsev was a Soviet Russian petroleum geologist. He is the founding father of modern abiogenic theory for origin of petroleum, which states that petroleum is formed from non-biological sources of hydrocarbons located deep in the Earth's crust and mantle.He graduated...
- Peak oilPeak oilPeak oil is the point in time when the maximum rate of global petroleum extraction is reached, after which the rate of production enters terminal decline. This concept is based on the observed production rates of individual oil wells, projected reserves and the combined production rate of a field...
- Thomas GoldThomas GoldThomas Gold was an Austrian-born astrophysicist, a professor of astronomy at Cornell University, a member of the U.S. National Academy of Sciences, and a Fellow of the Royal Society . Gold was one of three young Cambridge scientists who in the 1950s proposed the now mostly abandoned 'steady...
External links
- https://dco.gl.ciw.edu/ Deep Carbon Observatory
- "Geochemist Says Oil FieldsMay Be Refilled Naturally", New York Times article by Malcolm W. Browne, September 26, 1995
- "No Free Lunch, Part 1: A Critique of Thomas Gold's Claims for Abiotic Oil", by Jean Laherrere, in From The Wilderness
- "No Free Lunch, Part 2: If Abiotic Oil Exists, Where Is It?", by Dale Allen Pfeiffer, in From The Wilderness
- The Origin of Methane (and Oil) in the Crust of the Earth, Thomas Gold
- abstracts from AAPG Origin of Petroleum Conference 06/18/05 Calgary Alberta, Canada
- Gas Origin Theories to be Studied, Abiogenic Gas Debate 11:2002 (AAPG Explorer)]
- Gas Resources Corporation - J. F. Kenney's collection of documents