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10 novembre 2011 4 10 /11 /novembre /2011 01:49

Minor commercial and recreational uses

For its low solubility in nervous tissue, helium mixtures such as trimix, heliox and heliair are used for deep diving to reduce the effects of narcosis.Sony VAIO VPCZ11DGX/SJ Battery

At depths below 150 metres (490 ft) small amounts of hydrogen are added to a helium-oxygen mixture to counter the effects of high pressure nervous syndrome.[95] At these depths the low density of helium is found to considerably reduce the effort of breathing.Sony VAIO VPCZ11FHX/XQ Battery

Helium-neon lasers, a type of low-powered gas laser producing a red beam, had various practical applications which included barcode readers and laser pointers, before they were almost universally replaced by cheaper diode lasers.Sony VAIO VPCZ11V9R/B Battery

For its inertness and high thermal conductivity, neutron transparency, and because it does not form radioactive isotopes under reactor conditions, helium is used as a heat-transfer medium in some gas-cooled nuclear reactors.Sony VAIO VPCZ11X9E/B Battery

Helium, mixed with a heavier gas such as xenon, is useful for thermoacoustic refrigeration due to the resulting high heat capacity ratio and low Prandtl number. The inertness of helium has environmental advantages over conventional refrigeration systems which contribute to ozone depletion or global warming.Sony VAIO VPCZ11Z9E/B Battery

Scientific uses

The use of helium reduces the distorting effects of temperature variations in the space between lenses in some telescopes, due to its extremely low index of refraction.[5] This method is especially used in solar telescopes where a vacuum tight telescope tube would be too heavy.Sony VAIO VPCZ125GX/S Battery

Helium is a commonly used carrier gas for gas chromatography.

The age of rocks and minerals that contain uranium and thorium can be estimated by measuring the level of helium with a process known as helium dating.

Helium at low temperatures is used in cryogenics, and in certain crygenics applications. Sony VAIO VPCZ127FC Battery

As examples of applications, liquid helium is used to cool certain metals to the extremely low temperatures required for superconductivity, such as in superconducting magnets for magnetic resonance imaging. The Large Hadron Collider at CERNuses 96 metric tons of liquid helium to maintain the temperature at 1.9 kelvin.Sony VAIO VPCZ128GC Battery

Safety

Neutral helium at standard conditions is non-toxic, plays no biological role and is found in trace amounts in human blood. If enough helium is inhaled that oxygen needed for normal respiration is replaced, asphyxia is possible. Sony VAIO VPCZ12M9E/B Battery

The safety issues for cryogenic helium are similar to those of liquid nitrogen; its extremely low temperatures can result in cold burns and the liquid-to-gas expansion ratio can cause explosions if no pressure-relief devices are installed.

Containers of helium gas at 5 to 10 K should be handled as if they contain liquid helium due to the rapid and significant thermal expansion that occurs when helium gas at less than 10 K is warmed to room temperature.Sony VAIO VPCZ13M9E/B Battery

Biological effects

The speed of sound in helium is nearly three times the speed of sound in air. Because the fundamental frequency of a gas-filled cavity is proportional to the speed of sound in the gas, when helium is inhaled there is a corresponding increase in the pitches of the resonant frequencies of the vocal tract.Sony VAIO VPCZ13V9E/X Battery

This causes a reedy, duck-like vocal quality. (The opposite effect, lowering frequencies, can be obtained by inhaling a dense gas such as sulfur hexafluoride or xenon.)

Inhaling helium can be dangerous if done to excess, since helium is a simple asphyxiant and so displaces oxygen needed for normal respiration.Sony VAIO VPCZ13Z9E/X Battery

Breathing pure helium continuously causes death by asphyxiation within minutes. Inhaling helium directly from pressurized cylinders is extremely dangerous, as the high flow rate can result in barotrauma, fatally rupturing lung tissue.However, death caused by helium is rare, with only two fatalities reported between 2000 and 2004 in the United States.Sony VAIO VPCZZZHJ Battery

However, there were two cases in 2010, one in the USA in January and another in Northern Ireland in November.

At high pressures (more than about 20 atm or two MPa), a mixture of helium and oxygen (heliox) can lead to high-pressure nervous syndrome, a sort of reverse-anesthetic effect; adding a small amount of nitrogen to the mixture can alleviate the problem.Sony VAIO VPZ117 Battery

A fusion rocket is a theoretical design for a rocket driven by fusion power which could provide efficient and long-term acceleration in space without the need to carry a large fuel supply. The design relies on the development of fusion power technology beyond current capabilities, and the construction of rockets much larger and more complex than any current spacecraft.Sony VAIO VPZ118 Battery

A smaller and lighter fusion reactor might be possible in the future when more sophisticated methods have been devised to control magnetic confinement and prevent plasma instabilities.

For space flight, the main advantage of fusion would be the very high specific impulse, the main disadvantage the (probable) large mass of the reactor. Sony VAIO VPZ119 Battery

In addition, a fusion rocket may produce less radiation than a fission rocket, reducing the mass needed for shielding. The surest way of building a fusion rocket with current technology is to use hydrogen bombs as proposed in Project Orion, but such a spacecraft would also be massive.Sony VPCM11M1E/B Battery

Electricity generation vs. direct thrust

Many spacecraft propulsion methods such as ion thrusters require an input of electric power to run but are highly efficient. In some cases their maximum thrust is limited by the amount of power that can be generated (for example, a mass driver). Sony VPCM11M1E/W Battery

An electric generator that ran on fusion power could be installed purely to drive such a ship. One disadvantage is that conventional electricity production requires a low-temperature energy sink, which is difficult (i.e. heavy) in a spacecraft.Direct conversion of the kinetic energy of the fusion products into electricity is in principle possible and would mitigate this problem.Sony VPCM12M1E/L Battery

An attractive possibility is to simply direct the exhaust of fusion product out the back of the rocket to provide thrust without the intermediate production of electricity. This would be easier with some confinement schemes (e.g. magnetic mirrors) than with others (e.g. tokamaks). It is also more attractive for "advanced fuels" (see aneutronic fusion). Sony VPCM12M1E/P Battery

Helium-3 propulsion is a proposed method of spacecraft propulsion that uses the fusion of helium-3 atoms as a power source. Helium-3, an isotope of helium with two protons and one neutron, could be fused with deuterium in a reactor. The resulting energy release could be used to expel propellant out the back of the spacecraft. Sony VPCM12M1E/W Battery

Helium-3 is proposed as a power source for spacecraft mainly because of its abundance on the moon. Currently, scientists estimate that there are 1 million tons of helium-3 present on the moon, mainly due to solar wind colliding with the moon's surface and depositing it, among other elements, into the soil.Sony VPCM13M1E/L Battery

Only 20% of the power produced by the D-T reaction could be used this way; the other 80% is released in the form of neutrons which, because they cannot be directed by magnetic fields or solid walls, would be very difficult to use for thrust. Helium-3 is also produced via beta decay of tritium, which in turn can be produced from deuterium, lithium, or boron.Sony VPCM13M1E/P Battery

Even if a self-sustaining fusion reaction cannot be produced, it might be possible to use fusion to boost the efficiency of another propulsion system, such as aVASIMR engine.

Confinement concept

To sustain a fusion reaction, the plasma must be confined. The most widely studied configuration for terrestrial fusion is the tokamak, a form of magnetic confinement fusion.Sony VPCM13M1E/W Battery

Currently tokamaks weigh a great deal, so the thrust to weight ratio would seem unacceptable. NASA's Glenn Research Center has proposed a small aspect ratio spherical torus reactor for its "Discovery II" conceptual vehicle design. "Discovery II" could deliver a manned 172 000-kilogram payload to Jupiter in 118 days Sony VAIO VGN-Z11MN/B Battery

(or 212 days to Saturn) using 861 metric tons of hydrogen propellant, plus 11 metric tons of Helium-3-Deuterium (D-He3) fusion fuel.The hydrogen is heated by the fusion plasma debris to increase thrust, at a cost of reduced exhaust velocity (348–463 km/s) and hence increased propellant mass.Sony VAIO VGN-Z11VN/X Battery

The main alternative to magnetic confinement is inertial confinement fusion, such as that proposed by Project Daedalus. A small pellet of fusion fuel (with a diameter of a couple of millimeters) would be ignited by anelectron beam or a laser. To produce direct thrust, a magnetic field would form the pusher plate. Sony VAIO VGN-Z11WN/B Battery

In principle, the Helium-3 - Deuterium reaction or an aneutronic fusion reaction could be used to maximize the energy in charged particles and to minimize radiation, but it is highly questionable whether it is technically feasible to use these reactions. Both the detailed design studies in the 1970s, the Orion drive and Project Daedalus, used inertial confinement. Sony VAIO VGN-Z11XN/B Battery

In the 1980s, Lawrence Livermore National Laboratory and NASA studied an ICF-powered "Vehicle for Interplanetary Transport Applications" (VISTA). The conical VISTA spacecraft could deliver a 100-tonne payload to Mars orbit and return to Earth in 130 days, or to Jupiter orbit and back in 403 days. 41 tonnes of deuterium/tritium (D-T) fusion fuel would be required, plus 4124 tonnes of hydrogen expellant . The exhaust velocity would be 157km/s.Sony VAIO VGN-Z15 Battery

Magnetized target fusion (MTF) is a relatively new approach that combines the best features of the more widely studied magnetic confinement fusion (i.e. good energy confinement) and inertial confinement fusion (i.e. efficient compression heating and wall free containment of the fusing plasma) approaches.Sony VAIO VGN-Z15N Battery

Like the magnetic approach, the fusion fuel is confined at low density by magnetic fields while it is heated into a plasma, but like the inertial confinement approach, fusion is initiated by rapidly squeezing the target to dramatically increase fuel density, and thus temperature. MTF uses "plasma guns" Sony VAIO VGN-Z17 Battery

(i.e. electromagnetic acceleration techniques) instead of powerful lasers, leading to low cost and low weight compact reactors. The NASA/MSFC Human Outer Planets Exploration (HOPE) group has investigated a manned MTF propulsion spacecraft capable of delivering a 163 933-kilogram payload to Jupiter's moon Callisto using 106-165 metric tons of propellant (hydrogen plus either D-T or D-He3 fusion fuel) in 249–330 days.Sony VAIO VGN-Z17N Battery

This design would thus be considerably smaller and more fuel efficient due to its higher exhaust velocity (Isp=700 km/s) than the previously mentioned "Discovery II", "VISTA" concepts.

A popular confinement concept for fusion rockets is inertial electrostatic confinement, such as in the Farnsworth-Hirsch Fusor or the Polywell variation being researched by the Energy-Matter Conversion Corporation. Sony VAIO VGN-Z19 Battery

Dr. Robert Bussard published a series of technical articles discussing its application to spaceflight throughout the 1990s. His work was popularised by an article  in the Analog Science Fiction and Fact publication, where Tom Ligon (who has also written severalscience fiction stories) described how the fusor would make for a highly effective fusion rocket.Sony VAIO VGN-Z19N Battery

It was also featured in this role in the science fiction novel The Wreck of the River of Stars, by Michael Flynn. However, there are theoretical difficulties with the concept, related to energy losses via bremsstrahlung radiation and maintaining a highly non-Maxwellian ion energy distribution.Sony VAIO VGN-Z21MN/B Battery

A still more speculative concept is antimatter catalyzed nuclear pulse propulsion, which would use tiny quantities of antimatter to catalyze a fission and fusion reaction, allowing much smaller fusion explosions to be created.Sony VAIO VGN-Z21VN/X Battery

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.Sony VAIO VGN-Z21WN/B Battery

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.Sony VAIO VGN-Z21XN Battery

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,Sony VAIO VGN-Z21ZN/X Battery

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. Sony VAIO VGN-Z25 Battery

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.Sony VAIO VGN-Z25/B Battery

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 abiogenicpetroleum (liquid crude oil and long-chain hydrocarbon compounds).Sony VAIO VGN-Z25TN/B Battery

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%).Sony VAIO VGN-Z26TN/B Battery

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 oforganic chemistry, much less that of biochemistry, was established so the chemical nature of the petroleum was not known. Sony VAIO VGN-Z27 Battery

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. Sony VAIO VGN-Z27/B Battery

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.Sony VAIO VGN-Z27TN/X Battery

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 basalticsills to be solidified oils or bitumen. Sony VAIO VGN-Z29N Battery

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.Sony VAIO VGN-Z29N/X Battery

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.Sony VAIO VGN-Z31MN/B Battery

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.Sony VAIO VGN-Z31VN/X Battery

Currently, Jack Kenney of Gas Resources Corporation is a prominent proponent in the West.

Little research is directed on establishing abiogenic petroleum or methane, although the Carnegie Institution for Science have found that ethane and heavier hydrocarbons can be synthesized under conditions of the upper mantle. Sony VAIO VGN-Z31WN/B Battery

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.

  • rock porosity and migration pathways for abiogenic petroleum Sony VAIO VGN-Z31ZN/X Battery
  • ocean floor hydrothermal vents as in the Lost City hydrothermal field;
  • Mud volcanoes and the volatile contents of deep pelagic oozes and deep formation brines
  • mantle peridotite serpentinization reactions and other natural Fischer-Tropsch analogs
  • Primordial hydrocarbons in meteorites, comets, asteroids and the solid bodies of the solar system
    • Primordial or ancient sources of hydrocarbons or carbon in Earth Sony VAIO VGN-Z35 Battery
      • Primordial hydrocarbons formed from hydrolysis of metal carbides of the iron peak of cosmic elemental abundance (Cr, Fe, Ni, V, Mn, Co)
  • 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 (Ni, V, Cd, As, Pb, Zn, Hg and others)Sony VAIO VGN-Z35/B Battery

Similarly, research into the deep microbial hypothesis of hydrocarbon generation is advancing as part of the attempt to investigate the concept of panspermia andastrobiology, specifically using deep microbial life as an analog for life on Mars. Research applicable to deep microbial petroleum theories includes  Sony VAIO VGN-Z35TN/B Battery

  • 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 Sony VAIO VGN-Z36GD Battery

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 hydrocarbons, chiefly methane and as elemental carbon, carbon dioxide and carbonates.Sony VAIO VGN-Z36GD/B Battery

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. Sony VAIO VGN-Z36GD/J Battery

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.

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 lipids(fats, oils and waxes) into a waxy substance called kerogen.Sony VAIO VGN-Z36TD/B Battery

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.Sony VAIO VGN-Z36TD/J Battery

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.Sony VAIO VGN-Z37D Battery

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.Sony VAIO VGN-Z37D/B Battery

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 chondrites, contain carbonaceous material. Sony VAIO VGN-Z37GD Battery

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. Sony VAIO VGN-Z37GD/X Battery

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.Sony VAIO VGN-Z39D Battery

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.Sony VAIO VGN-Z39D/X Battery

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 Borehole. Sony VAIO VGN-Z41MD/B Battery

Data from the western United States suggests that aquifers from near the surface may extend to depths of 10 to 20 km. Hydrogen gas can be created by water reacting withsilicates, quartz and feldspar, in temperatures in the 25° to 270°C range. These minerals are common in crustal rocks such as granite. Sony VAIO VGN-Z41WD/B Battery

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.Sony VAIO VGN-Z45GD/B Battery

Serpentinite mechanism

One proposed mechanism by which abiogenic petroleum is formed was first proposed by the Ukrainian 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.Sony VAIO VGN-Z45TD/B Battery

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 processknown as the serpentinite mechanism or the serpentinite process.Sony VAIO VGN-Z46GD/B Battery

Serpentinites are ideal rocks to host this process as they are formed from peridotites and dunites, 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.Sony VAIO VGN-Z46GD/U Battery

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. Sony VAIO VGN-Z46MD/B Battery

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.Sony VAIO VGN-Z46SD/B Battery

Serpentinite synthesis

A chemical basis for the abiotic petroleum process is the serpentinization of peridotite, beginning with methanogenesis via hydrolysis of olivine into serpentine in the presence of carbon dioxide. Sony VAIO VGN-Z46TD/B Battery

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).

Evidence of abiogenic mechanisms

  • Calculations by J.F. Kenney using scaled particle theory for a simplified perturbed hard-chain, Sony VAIO VGN-Z46TD/R Battery
  • (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.Sony VAIO VGN-Z47GD/X Battery
  • 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 petroleum deposits within the Earth's rocks can be explained purely according to the orthodox view of petroleum geology. Sony VAIO VGN-Z48GD/X Battery

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. Sony VAIO VGN-Z48TD/X Battery

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.Sony VAIO VGN-Z51WG/B Battery

Microbial biomarkers

Thomas Gold, 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 biomarkers in extracted petroleum. Thorough rebuttal of biogenic origins based on biomarkers has been offered by Kenney, et al. (2001).Sony VAIO VGN-Z51XG/B Battery

Isotopic evidence

Methane 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). Sony VAIO VGN-Z530N/B Battery

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. ?13C 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.Sony VAIO VGN-Z540EBB Battery

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.Sony VAIO VGN-Z540NLB Battery

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 Raratio of less than 0.0001 that of the atmosphere.Sony VAIO VGN-Z540NMB Battery

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 ‰), Sony VAIO VGN-Z550N/B Battery

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.Sony VAIO VGN-Z55F Battery

Biomarker chemicals

Certain chemicals found in naturally occurring petroleum contain chemical and structural similarities to compounds found within many living organisms. These includeterpenoids, terpenes, pristane, phytane, cholestane, chlorins and porphyrins, which are large, chelating molecules in the same family as heme and chlorophyll.Sony VAIO VGN-Z55TG/B Battery

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.Sony VAIO VGN-Z56GG/B Battery

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.Sony VAIO VGN-Z56GG/E Battery

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.Sony VAIO VGN-Z56GGX Battery

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% vanadium pentoxide content in their ash, high enough that it is a commercial source for vanadium.Sony VAIO VGN-Z56TG/B Battery

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.Sony VAIO VGN-Z56TG/E Battery

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.Sony VAIO VGN-Z56TG/R Battery

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."Sony VAIO VGN-Z570N/B Battery

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.Sony VAIO VGN-Z57G Battery

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.Sony VAIO VGN-Z57GG/X Battery

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.Sony VAIO VGN-Z57GGX Battery

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.Sony VAIO VGN-Z57TG/X Battery

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.Sony VAIO VGN-Z58GG/X Battery

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 Field was determined to have abiogenic hydrocarbon production. Sony VAIO VGN-Z58GGX Battery

-sony-vaio-vgn-z58ggx-battery-27732.htm" title="Sony VAIO VGN-Z58GGX laptop battery">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."Sony VAIO VGN-Z590NJB Battery

Siljan Ring, Sweden

The Siljan Ring 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;Sony VAIO VGN-Z590UAB Battery

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.Sony VAIO VGN-Z591U/B Battery

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. Sony VAIO VGN-Z59G Battery

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.Sony VAIO VGN-Z620D Battery

This well also sampled over 13,000 feet (4,000 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.Sony VAIO VGN-Z620N/B Battery

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 petroleum .Sony VAIO VGN-Z650N/B Battery

Example proposed abiogenic methane deposits

Panhandle-Hugoton field (Anadarko Basin) in the south-central United States is the most important gas field with commercial helium content.

The B?ch H? 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.Sony VAIO VGN-Z670N/B Battery

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 basins of Hungary and Austria.Sony VAIO VGN-Z690CTO Battery

Natural gas pools interpreted as being mantle-derived are the Shengli Field and Songliao Basin, northeastern China.

The Chimaera gas seep, near Ç?ral?, 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. Sony VAIO VGN-Z690NAX Battery

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.Sony VAIO VGN-Z690PAB Battery

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.Sony VAIO VGN-Z690PCB Battery,Sony VAIO VGN-Z690PDB Battery,Sony VAIO VGN-Z690PEB Battery,Sony VAIO VGN-Z690PFB Battery,Sony VAIO VGN-Z690YAD Battery

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