Abiogenic petroleum origin

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"The capital fact to note is that petroleum was born in the depths of the Earth, and it is only there that we must seek its origin." (D. Mendeleev, 1877)

The theory of abiogenic petroleum origin states that petroleum (or crude oil) is primarily created from non-biological sources of hydrocarbons located deep in the crust of the Earth. The theory stands in contrast to the more widely held conventional view that petroleum is created from the remains of ancient living matter. The constituent precursors of petroleum (mainly methane) are commonplace and it is possible that appropriate conditions exist for hydrocarbons to be formed deep within the Earth.

Although this theory is supported by a large minority of geologists in Russia, where it was intensively developed in the 1950s and 1960s, it has only recently begun to receive attention in the West, where the biogenic theory is still believed by the vast majority of petroleum geologists. Planetary scientist Thomas Gold was one of the abiogenic theory's greatest proponents in recent years.[1] Although it was originally denied that abiogenic hydrocarbons exist at all on earth, this is now accepted by Western geologists. The orthodox position now is that while abiogenic hydrocarbons exist, they are not produced in commercially significant quantities, so that essentially all hydrocarbons that are extracted for use as fuel or raw materials would be biogenic.

The modern Russian-Ukrainian theory of petroleum, based on thermodynamic calculations, contends that petroleum is inorganic and formed at high pressures and temperature in the earth's mantle. This theory is said to be supported by experimental studies conducted by Dr J.F. Kenney and other Russian scientists. Their conclusions about petroleum origin are also said to vindicate the theories propounded by the geologist Nikolai Kudryavtsev.

A variation of the abiogenic theory includes alteration by microbes similar to those which form the basis of the ecology around deep hydrothermal vents.

One prediction of most abiogenic theories is that other planets of the solar system or their moons have large petroleum oceans, either from hydrocarbons present at the formation of the solar system, or subsequent chemical reactions.

That this theory is receiving increasing attention from Western geologists is indicated by the American Association of Petroleum Geologists having scheduled a conference [2] to meet in Vienna in July 2004 entitled "Origin of Petroleum—Biogenic and/or Abiogenic and Its Significance in Hydrocarbon Exploration and Production". The conference had to be canceled, however, due to financial considerations. Instead, AAPG held a one-day session on the topic at the June 2005 annual meeting in Calgary, Alberta. [3]

Comparison of theories

There are two theories on the origin of carbon fuels: the biogenic theory and the abiogenic theory. The two theories have been intensely debated since the 1860s, shortly after the discovery of widespread petroleum deposits. There are several differences between the biogenic and abiogenic theories.

Raw material

  • Biogenic: remnants of buried plant and animal life.
  • Abiogenic: deep carbon deposits from when the planet formed or subducted material.

Events before conversion

  • Biogenic: Large quantities of organic matter derived from dead plant and animal life were buried. Sediments accumulating over the material slowly compressed it and covered it. At a depth of several hundred meters, catagenesis converts it to bitumens and kerogens.
  • Abiogenic: At depths of hundreds of kilometers, carbon deposits are a mixture of hydrocarbon molecules which leak upward through the crust. Much of the material becomes methane.

Conversion to petroleum and methane

  • Biogenic: Catagenesis occurs as the depth of burial increases and the heat and pressure breaks down kerogens to form petroleum.
  • Abiogenic:
    1. When the material passes through temperatures at which extremophile microbes can survive some of it will be consumed and converted to heavier hydrocarbons.
    2. Another formulation of abiogenic origin theory sees microbial life strictly as a contaminant, unnecesary to account for any "biomarkers" supposedly supporting biogenic origins.[4] The full suite of hydrocarbons found in petroleum is generated at depth by abiogenic processes[5], and therefore shallow petroleum deposits represent the simple displacement of those hydrocarbons from their formation environment.

Formation of coal

  • Biogenic: Coal is organic material which was buried and compressed but did not undergo catagenesis into kerogens.
  • Abiogenic: Coal is organic material which was filled with hydrocarbons which seeped into the deposit. This can happen on the surface, such as in a swamp with methane and petroleum seeps.

Evidence supporting abiogenic theory

Supergiant oil fields

Russian geologist Nikolai Alexandrovitch Kudryavtsev was the first to propose the modern abiotic theory of petroleum. He studied the Athabasca Tar Sands in Alberta, Canada and concluded that no "source rocks" could form the enormous volume of hydrocarbons, and that therefore the only plausible explanation is abiotic deep petroleum.

Kudryavtsev was also a prominent and forceful advocate of the abiogenic theory. He argued that no petroleum resembling the chemical composition of natural crudes has ever been made from plant material in the laboratory under conditions resembling those in nature. He gave many examples of substantial and sometimes commercial quantities of petroleum being found in crystalline or metamorphic basements, or in sediments directly overlying those. He cited cases in Kansas, California, Western Venezuela and Morocco. He also pointed out that oil pools in sedimentary strata are often related to fractures in the basement directly below. This is evidenced by the Ghawar supergiant oil field (Saudi Arabia); the Panhandle Field in Kansas (United States), which also produces helium; the Tengiz Field (Kazakhstan); the White Tiger Field (Vietnam); and innumerable others. The Lost Soldier Field in Wyoming has oil pools, he stated, at every horizon of the geological section, from the Cambrian sandstone overlying the basement to the upper Cretaceous deposits. A flow of oil was also obtained from the basement itself. Hydrocarbon gases, he noted, are not rare in igneous and metamorphic rocks of the Canadian Shield. Petroleum in Precambrian gneiss is encountered in wells on the eastern shore of Lake Baikal. He stressed that petroleum is present, in large or small quantity, but in all horizons below any petroleum accumulation, apparently totally independent of the varied conditions of formation of these horizons. This statement has since become known as "Kudryavtsev's Rule" and many examples of it have been noted in different parts of the world. He concluded that commercial accumulations are simply found where permeable zones are overlaid by impermeable ones.

Kudryavtsev introduced a number of other relevant considerations into the argument. Columns of flames have been seen during the eruptions of some volcanoes, sometimes reaching 500 meters in height, such as during the eruption of Merapi in Sumatra in 1932. (There have been several other instances subsequently.) The eruptions of mud-volcanoes have liberated such large quantities of methane that even the most prolific gasfield underneath should have been exhausted long ago. Also the quantities of mud deposited in some cases would have required eruptions of much more gas than is known in any gasfield anywhere. The water coming up in some instances carries such substances as iodine, bromine and boron that could not have been derived from local sediments, and that exceed the concentrations in seawater one hundred fold. Mud volcanoes are often associated with lava volcanoes, and the typical relationship is that where they are close, the mud volcanoes emit incombustible gases, while the ones further away emit methane. He knew of the occurrence of oil in basement rocks of the Kola Peninsula, and of the surface seeps of oil in the Siljan Ring formation of Central Sweden (which we shall discuss later). He noted as mentioned above that the enormous quantities of hydrocarbons in the Athabasca tar sands in Canada would have required vast amounts of source rocks for their generation in the conventional discussion, when in fact no source rocks have been found.

Existence of hydrocarbon deposits

The world’s conventional oil reserves should disappear in no more than one million years, based upon the rate of hydrocarbon seepages.[6] If there is a limited source of hydrocarbon deposits, in geologic time frames, it is an extraordinary coincidence that deposits exist now. If such deposits are being replenished, their existence becomes less surprising.

Cold planetary formation

In the late 19th century it was believed that the Earth was extremely hot, possibly completely molten, during its formation. One reason for this was that a cooling, shrinking, planet was necessary in order to explain geologic changes such as mountain formation. A hot planet would have caused methane and other hydrocarbons to be outgassed and oxidized into carbon dioxide and water, thus there would be no carbon remaining under the surface. Planetary science now recognizes that formation was a relatively cool process until radioactive materials accumulate together deep in the planet.

  • Recent testing of a zircon, at 4.4 billion years old the world's oldest rock, suggests rocks which formed at temperatures low enough for liquid water. The Moon formed only shortly before this time. [7]

Known hydrocarbon sources

Carbonaceous chondrite meteorites contain kerogen-like carbon and hydrocarbons. Heated under pressure, this material would release hydrocarbon fluids in addition to creating solid carbon deposits. Further, at least ten bodies in our solar system are known to contain at least traces of hydrocarbons.

Meteorite ALH84001, believed to be from Mars, contains carbonate minerals which were formed about 3.9 billion years ago. The deposits are in igneous rock. On Earth, microorganisms often create carbonates. However, the material could also have been formed by water carrying carbon dioxide, or by hot carbon-dioxide-bearing fluids.

Kerogen-like material has also been detected in interstellar clouds and dust particles around stars.

Methane on Earth

Methane is typically found on Earth, when not in gas deposits, in methane hydrate deposits under high pressure under deep abyssal plains of oceans, ostensibly forming from the decay of sinking biotic materials.

Methane not on Earth

Methane has been detected or is believed to exist in several locations of the solar system. It is believed to have been created by abiotic processes, except possibly on Mars.

In 2004, the Cassini spacecraft confirmed methane clouds and hydrocarbons on Titan, a moon of Saturn.

Traces of methane gas also are in the thin atmosphere of the Earth's Moon.

Methane has also been detected in interstellar clouds.

Unusual deposits

Hydrocarbon deposits have been found in places that are said to be poorly explained by biogenic theory. Some oil fields are being refilled from deep sources, although this does not rule out a deep biogenic source rock. In the White Tiger field in Vietnam and many wells in Russia, oil and natural gas are being produced from reservoirs in granite basement rock. In the Vietnamese case, this rock is believed to have no oil-producing sediments under it, so the biogenic theory requires the oil to have migrated laterally dozens of kilometers along faults from source rock.

Deep microbes

Microbial life has been discovered 4.2 kilometers deep in Alaska and 5.2 kilometers deep in Sweden. Methanophile organisms have been known for some time, and recently it was found that microbial life in Yellowstone National Park is based on hydrogen metabolism. Other deep and hot extremophile organisms continue to be discovered. Proponents of abiogenic petroleum origin contend that deep microbial life is responsible for the biomarkers (see below) that are generally cited as evidence of biogenic origin.

U.S. Geological Survey (USGS) scientist Frank Chapelle and his colleagues from the USGS and the University of Massachusetts have discovered a potential analog for life on other planets. A community of Archaea is thriving deep in the subsurface source of a hot spring in Idaho. Geothermal hydrogen, not organic carbon, is the primary energy source for this methanogen-dominated microbial community. This is the first documented case of a microbial community completely dominated by Archaea.[8]

Helium

Helium gas has close association with petroleum. Although ³He is primordial, much He gas is from radioactive decay of uranium. Helium gas is associated with light oils, sometimes accompanied by nitrogen that allow petroleum to reach shallow levels in crust.

Hydrogen

Petroleum is composed mainly of n-alkanes. Sir Robert Robinson, Nobel Laureate in chemistry, studied the chemical make-up of natural petroleums in great detail, and concluded that they were mostly far too hydrogen-rich to be a likely product of the decay of plant debris. Olefins (n-alkenes), 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."

Trace metals

Nickel (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% in vanadium pentoxide in their ash, high enough that it is a commercial souce for vanadium. These metals are common in earth´s mantle.

Analysis of 22 trace elements in 77 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.[9]

Diamondoids

Tiny diamondoids occur in oils and condensates. They have similar diamond structure and suspected to have similar origins related to kimberlite diamond deposits, from hot and high pressure rocks in the earth´s mantle.

Thermodynamics

The Second Law of Thermodynamics prohibits spontaneous generation of hydrocarbons heavier than methane at low pressures. Thermodynamic calculations[10] and experimental studies confirm that n-alkanes (common petroleum components) do not spontaneously evolve from methane at pressures typically found in sedimentary basins, and so the theory of an abiogenic origin of hydrocarbons suggests deep generation (below 200 km [11].)

Biology

Template:Sectionclean Life as we know it is mainly based on carbon. First living organisms (archaeobacteria) of course needed food and this food at least was primordial methane or petroleum (hydrocarbons). They live at deep levels in crust and they formed oil contaminants which also became parts of biomarkers found in natural petroleum. Photosynthesys is a very complicated process that primitive organisms got to achieve the surface of our planet, probably this situation occurred with its evolution seeking for food when hydrocarbon upwelling locally ceased, then making your own food, i.e. autotrophs.

Serpentinization and chemical synthesis of oil

Deep sea vent biogeochemical cycle diagram

Another possible formation of inorganic oil is via Fischer-Tropsch Synthesis. The Fischer-Tropsch process converts carbon dioxide, carbon monoxide, and methane into liquid hydrocarbons of various forms. The carbon dioxide and carbon monoxide is generated by partial oxidation of coal and wood-based fuels. This process was developed and used extensively in World War II by Germany, which had limited access to crude oil supplies. It is today used in South Africa to produce most of that country's diesel from coal. Since there are large but finite coal reserves in the world, this technology could be used as an interim transportation fuel if conventional oil were to disappear. There are several companies developing the process to enable practical exploitation of so-called stranded gas reserves, those reserves which are impractical to exploit with conventional gas pipelines and LNG technology.

Serpentinization of carbon-rich peridotite ultramafic rocks involving Fischer-Tropsch reactions are thought to occur within the crust of the earth when mantle peridotite is hydrolysed becoming serpentinite while releasing hydrogen. In the presence of catalyst transition metals (e.g. Fe, Ni) hydrogen reacts with carbon dioxide from carbonate rocks and results in n-alkane hydrocarbons, including linear saturated hydrocarbons, alcohols, aldehydes, ketones, aromatics, and cyclic compounds.[12] Nanodiamonds in mineral fuels suggest contact with material with such a deep hot history. Where hydrocarbon fluids encounter shelf limestones, extensive replacement reactions occur which form large volumes of hydrothermal dolomite.[13]

Deep structures and petroleum association

Petroleum is found in close correlation to deep structures in the earth, mainly over crustal plate limits (convergent as subduction or continental collision and divergent boundaries). This correlation is confirmed by the distribuition of oil fields along the arcs, for instance, of Indonesia, the Persian Gulf, the Apennines in Italy (gas and oil fields), Alaska, the Barbados Arc continuing towards Trinidad & Tobago and Venezuela, the Atlantic rift (passive margin basins (South America Brazil and Africa) and others riftogenic basins. Oil and gas fields always show a connection with large-scale basement structures below. Further, petroleum is found at meteorite impact structures because faults can reach the earth's mantle.

Why is oil frequently found in sedimentary basins?

Hydrocarbons rise from great depth due to their buoyancy, accumulating when they encounter impermeable caprock such as shale. These accumulations within porous strata are the most economical places to mine petroleum. Traditional biogenic theory also predicts such accumulations in sedimentary strata (as a formation environment), so a confirmation bias may have developed in the oil exploration industry.

Most fluid motion within rock occurs along fractures, so hydrocarbons preferentially rise through the deep fracture networks associated with plate boundaries.

Ambiguous results

Ongoing research has changed the status of some information. For example, some biomarkers which were interpreted as evidence supporting the biogenic theory have been undermined by finding similar materials in thermophilic situations which are part of abiogenic theories.

Biomarkers

Chemicals of biological origin have been found in many geologic hydrocarbon deposits. These biomarkers were believed to be from known surface sources. Due to the difficulty in culturing and sampling deep heat-loving bacteria, thermophiles, little was known of their chemistry. As more is learned of bacterial chemistry, more biomarkers seem likely to be due to bacterial action. Hopanoids, called the 'most abundant natural products on Earth', were believed to be indicators of oil derived from ferns and lichens but are now known to be created by many bacteria, including archaea. Sterane was thought to have come from processes involving surface deposits but is now known to be produced by several prokaryotes including methanotrophic proteobacteria. Thorough rebuttal of biogenic origins based on biomarkers has been offered by Kenney, et al. (2001)[14].

Deep hot carbon sources

Carbonate lava

Carbonatites are intrusive carbonate-mineral-rich igneous rocks. Although they are deposits of carbon from an igneous source, the geology behind their creation is not understood.

Hydrothermal vents

Hydrothermal vents expel mineral-rich geothermally heated water.

  • Carbon dioxide abiogenically produced from magma: As magma outgasses helium and carbon dioxide at depths less than 60 km, there should be deep carbon fluids present in areas such as oceanic ridges where the magma is able to heat surface waters.
  • Microbes can create methane: Extremophile methanogens such as Methanopyrus can convert CO2 to methane.
  • Methane can also be created chemically: Iron in rock can release hydrogen from water, then carbon dioxide can combine with the hydrogen to produce methane and water. University of Minnesota researchers discovered that rocks rich in chromium minerals can encourage chemical methane production, while also producing the more complex hydrocarbons ethane and propane.
  • Methane and carbon dioxide may be dissolved in water which enters hydrothermal vent systems.
  • Hydrothermal vents might release methane and carbon from deposits of biological origin, although this is less likely in vents at spreading oceanic ridges.

Evidence supporting biogenic theory

Unusual deposits

While it is true that some oil fields do not conform to the standard model of a fixed amount of oil trapped in a sedimentary basin, these examples are accommodated by the biogenic model. For example, the White Tiger field (Cuu Long Basin) cited above is located in an area where significant normal faulting brings relatively young sedimentary rocks into contact with older, fractured horst blocks of igneous rocks.[15] The produced oil is described as typically lacustrine (derived from lake deposits), consistent with the migration of hydrocarbons from the organic-rich sediments into the fractured basement.

In Eugene Island 330, a large production area of that is currently being recharged, a deep source rock is indicated, and the chemical composition of the recharging oil strongly indicates that it is leaking from a deep, intermediate reservoir.

US continuous hydrocarbon reservoirs.

One type of unusual deposit that one might to expect to find if the abiogenic hypothesis is true would be hydrocarbons trapped in sedimentary basins that do not contain conventional source rocks. Evidence for such deposits is lacking. Many economically disappointing wells have been drilled into geologic structures that would be expected to trap hydrocarbons, but there are no hydrocarbons present. Oil companies have learned that an appropriate source rock is necessary before they will commit to drilling a well in a potential new field.

Biomarkers

It has been argued that the abiogenic theory does not explain the detection of various biomarkers in petroleum. Microbial consumption does not yet explain some trace chemicals found in deposits. Materials which suggest certain biological processes include tetracyclic diterpane and oleanane. Although extremophile microorganisms exist deep underground and some metabolize carbon, some of these biomarkers are only known so far to be created in surface plants. This evidence is consistent with the biogenic hypothesis, although it might be true that these hydrocarbons have merely been in contact with ancient plant residues. There also is evidence that low-temperature relatives of hyperthermophiles are widespread, so it is also possible for biological deposits to have been altered by low-temperature bacteria which are similar to deeper heat-loving relatives. One study found diamondoids in oil show high levels of carbon isotopic fractionation the same as most true biomarkers, indicating diamondoid derivation from enzymatically-created lipids.[16]


Petroleum origin, peak oil, and politics

Many aspects of the abiogenic theory were developed in the former Soviet Union by Russian and Ukrainian scientists during the Cold War. Some proponents see a pro-Western bias in the promotion of the biogenic theory. Thus, in addition to the scientific merits of competing hypothoses, political and economic considerations often influence discussions of petroleum origins.

The topic of the origin of petroleum is also linked to discussions of projected declines in petroleum production, variously referred to with such terms as "peak oil" or "Hubbert's peak". Some environmentalists accuse abiogenic theory supporters of a "cornucopian" worldview. They claim that such a view incorrectly sees no limits to exploitation of petroleum supplies while simultaneously ignoring potential consequences of petroleum consumption such as global warming. Conversely, some supporters of the abiogenic theory accuse their opponents of an unwarranted Malthusian viewpoint that needlessly limits the use of hydrocarbons as an energy source and artificially inflates oil prices.

Independent of whether massive hydrocarbon reserves exist deep in the crust, they are unattainable in the short term. Considering the apparent dominance of the biogenic origin theory in the exploration industry, new oil discoveries based on abiogenic theory may be slow in coming. A new prediction by Goldman Sachs picks 2007 for peak global oil production, so it is unlikely that the serious economic ramifications of peak oil can be avoided. For this reason, as well as concerns about global warming, development of nuclear power and renewable energy sources continues at an accelerating pace.

These aspects of the controversy may be seen in many of the online articles in the External links section below.

See also

References

  1. ^ . ISBN 0387985468. {{cite book}}: Missing or empty |title= (help); Unknown parameter |Author= ignored (|author= suggested) (help); Unknown parameter |Publisher= ignored (|publisher= suggested) (help); Unknown parameter |Title= ignored (|title= suggested) (help); Unknown parameter |Year= ignored (|year= suggested) (help)
  2. ^ "New AAPG Hedberg Conference in Vienna". AAPG. April 15. {{cite web}}: Check date values in: |date= and |year= / |date= mismatch (help)
  3. ^ Template:Journal reference doi:10.1130/0091-7613(2002)030<0351:ACEE>2.0.CO;2 "A Cool Early Earth". Zircons Are Forever. April 11. {{cite web}}: Check date values in: |date= and |year= / |date= mismatch (help)
  4. ^ Template:Journal reference doi:10.1038/415312a
  5. ^ "The Prohibition of Hydrocarbon Genesis at Low Pressures". Gas Resources Corporation. April 15. {{cite web}}: Check date values in: |date= and |year= / |date= mismatch (help)
  6. ^ Template:Journal reference Article link
  7. ^ Template:Journal reference issue Article link
  8. ^ Template:Journal reference Article link
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