One of those ‘A’ shows up and causes a “Ding Ding!” connection to ‘B’ questions.
Frequently folks wonder where oil comes from. We’ve got the dinosaur juice folks ( really ancient algae sinking in shallow stagnant seas) and we’ve got the abiogenic folks who often assert it’s the byproduct of some kind of geologic process such as a FT conversion from the breakdown of subducting carbonate rocks.
On occasion the abiogenic folks will point at the methane lakes on Titan and say “See, it’s natural and needs no dead dinosaurs” (or algae).
Well, I’m going to propose a third possible for consideration. What if it IS fossil fuel (in that it is ancient in origin) but is abiogenic in origin; originally made by a process that is no longer happening? We could still see much of what we see today. Distribution in non-sedementary locations (as found by the abiogenic Russian school) yet not still being created (old and subject to depletion fossil source). What if we are hotter and more heavily subject to UV and that caused the methane lakes to become oil lakes?
A Crude Question
Step One: What is the size and chemical composition of crude oil, in gross terms?
It ranges from very light, to stuff like heavy asphalt. It is widely believed that the asphalt like stuff is the result of a long ‘cooking time’ in the rocks and / or evaporation of light ends. We also find natural gas which is essentially very light hydrocarbons.
On a semi-random web search I turned up this patent application that describes the typical weight, in Daltons, of crude oil molecules and notes that it often contains nitrogen.
Crude oil extracted from reservoir rock contain a number of undesired compounds, or contaminants. Reduction in the amount of sulfur compounds in automotive fuels and other refined hydrocarbons are required in order to meet environment concernsand regulations. These contaminants also adversely impact refinery operations, e.g., by poisoning catalysts.
Crude oils contain heteroatoms such as sulfur, nitrogen, nickel, vanadium and others in quantities that impact the refinery processing of the crude oils fractions. Light crude oils or codensates contain in concentrations as low as 0.01 W %. Incontrast, heavy crude oils contain as much as 5-6 W %. The nitrogen content of crude oils can range from 0.001-1.0 W %. The heteroatom contents of typical Arabian crude oils are listed in Table 1 from which it can be seen that the heteroatom content ofthe crude oils within the same family increases with decreasing API gravity, or increasing heaviness.
TABLE-US-00001 TABLE 1 Property ASL AEL AL AM AH Gravity, .degree. 51.4 39.5 33.0 31.1 27.6 Sulfur, W % 0.05 1.07 1.83 2.42 2.94 Nitrogen, ppmw 70 446 1064 1417 1651 RCR, W % 0.51 1.72 3.87 5.27 7.62 Ni + V, ppmw <0.1 2.9 21 34.0 67
The following abbreviations are used in Table 1: ASL–Arab Super Light; AEL–Arab Extra Light; AL–Arab Light; AM–Arab Medium and AH–Arab Heavy; W % is percent by weight; ppmw is parts per million by weight.
The heteroatom content of the crude oil fractions also increases with increasing boiling point and representative data is provided in Table 2.
TABLE-US-00002 TABLE 2 Fractions, .degree. C. Sulfur WT % Nitrogen ppmw C5-90 0.01 93-160 0.03 160-204 0.06 204-260 0.34 260-315 1.11 315-370 2.00 253 370-430 2.06 412 430-482 2.65 848 482-570 3.09 1337
A custom-built FT-ICR ultra high resolution mass spectrometer, equipped with a 9.4 Tesla superconducting magnet was used to characterize the crude oil and the upgraded products. The observed masses in the spectra of feedstock and product rangefrom 200 up to 800 Daltons for the three ionization modes employed. Neutral species. i.e., aromatic hydrocarbons and sulfur aromatic species were detected using the APPI ionization mode. Polar nitrogen and oxygen species were ionized by electrosprayin the positive and negative mode, respectively.
Aromatic hydrocarbon, sulfur, nitrogen, and oxygen species are all identified in both feedstock and product. Mono-, di- and tri-sulfur species with a high degree of aromatic character, i.e., five to seven condensed aromatic rings, are found inthe feedstock, but are readily removed by the upgrading treatment. Molecules with fewer than five condensed aromatic rings are proportionally increased as a result of the upgrading process of the invention.
There is a real stew of chemicals, but a significant number of aromatic rings and a variable, but also significant, quantity of nitrogen included. The presence of nitrogen and sulphur is often taken to indicate biologic origin as those elements often are present in biological compounds. But is there another source?
On Solar System Bodies
Step Two: What happens elsewhere in non-biologic bodies?
Tholin [after the ancient Greek word θολός (tholós) meaning “not clear”] is a heteropolymer molecule formed by solar ultraviolet irradiation of simple organic compounds such as methane or ethane. Tholins do not form naturally on modern-day Earth, but are found in great abundance on the surface of icy bodies in the outer solar system. They usually have a reddish-brown appearance.
Tholins have also been detected in the stellar system of an eight-million-year-old star known as HR 4796A using the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) aboard the Hubble Space Telescope. HR 4796A is 220 light years from Earth.
“Triton tholin” and “Titan tholin” are nitrogen-rich organic substances produced by the irradiation of gaseous mixtures of nitrogen and methane such as that found in those moons’ atmospheres; Triton’s atmosphere is 99.9% nitrogen and 0.1% methane and Titan’s atmosphere is 98.4% nitrogen and the remaining 1.6% composed of methane and trace amounts of other gases. These atmospherically derived substances are distinct from “ice tholin”, which is formed by irradiation of clathrates of water and organic compounds such as methane or ethane. The plutino Ixion is also high in this compound.
The surfaces of comets, centaurs, and many icy moons in the outer solar system are rich in deposits of Triton, Titan and ice tholins. The haze and orange-red color of Titan’s atmosphere and centaur-class planetoids are thought to be caused by the presence of tholins. Tholins may also have been detected in the protoplanetary disks of young stars; see HR 4796A. Some researchers have speculated that Earth may have been seeded by organic compounds early in its development by tholin-rich comets, providing the raw material necessary for life to develop; see Urey-Miller experiment for discussion related to this issue. Tholins do not exist naturally on current-day Earth due to the oxidizing character of the free oxygen component of its atmosphere ever since the Great Oxygenation Event around 2400 million years ago.
A theoretical model explains formation of tholins by the dissociation and ionization of molecular nitrogen and methane by energetic particles and solar radiation, formation of ethylene, ethane, acetylene, hydrogen cyanide, and other small simple molecules and small positive ions, further formation of benzene and other organic molecules, their polymerization and formation of aerosol of heavier molecules, which then coagulate and deposit on the planetary surface.
The term "tholin" was coined by astronomer Carl Sagan to describe the difficult-to-characterize substances he obtained in his Urey-Miller-type experiments on the gas mixtures that are found in Titan's atmosphere. It is not a specific compound but is a term generally used to describe the reddish, organic component of planetary surfaces.
Tholins formed at low pressure tend to contain nitrogen atoms in the interior of their molecules, while tholins formed at high pressure are more likely to have nitrogen atoms located in terminal positions.
Tholins can act as an effective screen for ultraviolet radiation, protecting the planetary surface from it.
A wide variety of soil bacteria are able to use tholins as their sole source of carbon. It is thought tholins may have been the first microbial food for heterotrophic microorganisms before autotrophy evolved.
One of the common assertions is that life had to evolve in the oceans due to the high UV levels on the surface. But what if that surface were protected by tholins?
We have this semi-ubiquitous stuff, that sure sounds a lot like oil, even down to color and having various nitrogen compounds in it. It is conducive to protecting life, and bugs in the soil today find it yummy. Hmmm… Oh, and the Dalton range is about the same as crude oil up to tar like ranges.
It may even be that the existence of life argues for such an early world form.
The PAH world hypothesis is a speculative hypothesis that proposes that polycyclic aromatic hydrocarbons (PAH), assumed to be abundant in the primordial soup of the early Earth, played a major role in the origin of life by mediating the synthesis of RNA molecules, leading into the RNA world. As of yet, it is untested.
We have soil bacteria that are happy to live on dirty oil or even tholins. We have an existence proof of the stuff being made on other worlds today in a non-oxygen atmosphere. We have a plausible theory that life would more easily evolve in a world full of hydrocarbons. We know the early Earth was non-oxygen and only formed an oxygen atmosphere much later after life was well established. We know the early Earth had the needed materials in the early atmosphere and we know that UV was present prior to the oxygen atmosphere making Ozone to block the UV.
It looks to me like a very simple chain of causality would have the early Earth being rather like those other methane rich atmospheres. Complex hydrocarbons form, raining out, and forming underground reservoirs (rather like water does today). Life forms. Eventually our oxygen atmosphere forms and any hydrocarbons remaining in the atmosphere oxidize to CO2. We are left with the residual hydrocarbons deep underground in anoxic conditions.
In that context, it would mean that at one time we had oil raining from the sky, and it would imply that some of the present oil deposits are fossil deposits from that age. (Most likely oil in rocks younger than the Oxygen Event of about 2.5 Billion Years Ago would be from other sources such as biogenic or geologic, or was ancient oil that migrated to those locations after formation.) But do we really know how old various oil deposits might be? The present thesis is that it migrates from ‘source rocks’ to where we find it. Dating is complicated by that, and by soil radiation. As many locations (like Texas) are relatively young, the theory is that the oil is young too. But could it have simply “leaked up” from very deep and very old sources?
Could some of the oil have fallen as rain 2.5+ Billion Years Ago?
No, I don’t have an answer. Just an interesting question. ( I’m still pretty sure a lot of the oil is squashed and heated algae, and think some of it is FT Cooked Carbonate rocks run over mineral catalysts like zeolite. But I can’t see any reason why the early Earth would not have Organic Rain…