Where does oil come from?


With apologies to Soundgarden, our cars aren't burning dinosaur bones.

Instead, most scientists think oil started out as plankton and other tiny ocean critters, specifically their lipids—tough, stringy molecules that bacteria want to eat about as much as you enjoy dining on gristle or tendons. The idea is that, unlike the rest of the biologic material, lipids don't get gobbled up by bacteria, instead falling out to the bottom of the ocean, where they're covered by millions of years of sediment and eventually become oil. One researcher told LiveScience that some petroleum molecules actually resemble lipids found in cell membranes.

Interestingly, there's a small faction of researchers who say petroleum isn't the fossil fuel everybody thinks. This theory—that the carbon precursor of oil has nothing to do with decomposing organisms, has existed deep within the Earth probably since the planet formed and seeps upward through the mantle—was popular in Soviet Russia, but doesn't match up with what we know about the composition of petroleum and where deposits are likely to be found. That said, recent research has shown that it's theoretically possible for certain hydrocarbons to be synthesized under conditions found in the Earth's mantle. So the mechanism is realistic, even if there's no evidence that petroleum is really being produced this way.

Image courtesy Flickr user richardmasoner, via CC



    1. Yes, damnit! You could use mildly contaminated sewage as a feedstock for the process.

      Not to mention animal waste . . . all those lagoons of pig shit could be put to good use.

  1. I first heard of the “abiotic” oil-origin theory from a cranky (obnoxious, confrontational) libertarian SF fan. “Your knowledge is defective! The oil wells are refilling from the bottom!” was the line I remember. This was years before Gold’s book came out.

    I think it’s a theory favored mostly by folks who are philosophically offended by the idea of conservation and limits to growth.

  2. There are some huge problems explaining a pile of things when it comes to abiogenic oil. While it seems clear that at least SOME hydrocarbon reserves are not from “traditional” biological deposits, saying most- or all- are abiogenic just doesn’t seem right. For one thing, the pristane and phytane components would have to be explained away- ditto with why there are higher concentrations of molecules with even numbered carbons in their backbone than odd numbered carbons. The even-numbered carbons fits a biological source, while a ratio closer to parity would be more readily explained by an abiogenic origin- why would abiogenic oil have less C7, C9, C11… than C6, C8, C10…? It just doesn’t jibe.

    Anyway- I’m just a geologist; my training is old. Maybe there are better data on this kind of stuff now, I dunno. But bear in mind that oil can travel very far from its reservoir rock, which is one reason it might be found in old volcanic rocks. That doesn’t mean people have gotten rich sticking wells into volcanic necks; the oil just isn’t there.

    1. The whole idea of Gold’s book (Deep Hot Biosphere) was that so-called fossil fuels are actually being created by a biosphere which is feeding off of abiogenic minerals and gases. I read DHB a few weeks ago, and it’s somewhat compelling – mostly because the fossil fuel explanation has a large number of gaps in it.

      I went into the Minneapolis Science Museum the other day, and saw their display on fossil fuels which basically went:

      1. Plants die
      2. ????
      3. Oil

  3. The concept that oil comes from melted dinosaurs comes from the brilliant Chevron commercial by animator, Bob Kurtz from the late 70s. See it here (along with other great Kurtz and Friends animation)…

    Bob Kurtz Historical Commercial Reel

    I spoke to Bob about this spot and he said that he almost didn’t do it, but decided that the message to conserve energy was a good one. Chevron sent a note telling him to cut out the dinos because oil wasn’t made of them, but it was such an irresistible visual it ended up staying.

  4. Isn’t the solar system full of hydrocarbons like methane and ethane and propane on Titan and Neptune for example? Why couldn’t that also happen on Earth?

    1. Those are relatively simple gasses. We have them on Earth, too.

      Petroleum is pretty unusual stuff. Long complex molecules.

    2. I see this question a lot: why do we see hydrocarbons on other planets and moons that are thought not to have life, but they are associated with biology on Earth, and it’s a fair one, so I’ll try to give simple answer. In the parlance of chemistry, methane is a simple “reduced” molecule that carbon likes to form whereas carbon dioxide is the “oxidized” form. During planet formation, in the outer solar system where the temperatures are very cold, the formation of reduced carbon (CH4) was favored over oxidized carbon (CO2). In the inner solar system where it is much hotter, oxidized carbon was favored, so a moon like Titan (and outer planets and comets) ended up with significant amounts of methane, whereas Venus, Earth, and Mars ended up with atmospheres mostly made of CO2. I’m simplifying a bit, because CO2 (and CO) are found in the outer solar system, and hydrocarbons may have been delivered to the early Earth (probably from objects originating from colder parts of the protosolar nebula). But in general, in the cold outer solar system carbon likes to make methane, and in the hot inner solar system, carbon likes to make CO2.

      The other reason is that methane is susceptible to decomposition in an atmosphere by solar UV radiation. In the inner solar system, closer to the Sun, solar UV breaks down CH4 molecules very quickly. Methane in the atmosphere goes away on timescales of thousands of years. On Titan, the amount of UV is much less, so methane can exist in the atmosphere for millions of years. In fact, UV radiation allows for a very slow, but important, series of chemical reactions in Titan’s atmosphere. With lots of primordial methane to work with, solar UV turn CH4 into heavier hydrocarbons, like ethane, propane, butane, benzene, etc. There’s not enough methane abundance or time in Earth’s atmosphere for something similar to happen.

  5. There is a The Teaching Company course on Geology where the lecturer talks about the abiotic origin of oil, and maybe life. It provides some arguments on the subject inclunding experiments on creating organic compounds from inorganic ones under extreme pressures in the lab.He also says that the fact that oil is explored only on sedimentary terrain is just a matter of economics, since to drill crystalline rocks would be too dificult and expensive and it wouldn’t be cost-effective while there is so many sites easier to explore. There is much more on the subject on the course. I’m not sure but I think it is this one: http://www.teach12.com/ttcx/coursedesclong2.aspx?cid=1700

    There was also a special issue of Newsweek on the oil subject some years ago that deal with the origin and abudance issues.

  6. LOL to Xeni! I’m still reeling from including juggalette to my pop vocab…and waking nightmares….

    And wait, I knew it wasn’t dinosaur bones, but I thought it WAS dinosaur pee.

  7. A couple years ago I had a very intelligent, and somewhat cranky professor. One of the many things that still sticks out in my mind was “If you lock a group of scientists and geologists in a room with a gun and tell them to come out when everyone inside agrees how oil is formed you’ll hear gunshots until the last person left either leaves the room, or shoots themself.”

    It was understood that they would be shooting from not being completely certain about their answer.

  8. Another problem with the abiotic hypothesis is that the carbon isotopic signature of petroleum is similar to that of biotic carbon, but not to mantle carbon, which is heavier.

  9. My understanding was that temperature wasn’t the deciding factor, but availability of hydrogen. There was lots in the early solar system and on giant planets, so oxygen prefers to form water, leaving carbon to form methane.

    In atmospheres of smaller planets and moons, hydrogen gets zapped off of molecules as you said and floats away. That leaves oxygen to form carbon dioxide. I think this is still the common form on Titan, but because of the temperature it’s a solid, rather than part of the atmosphere.

    Last I heard the presence of methane on Titan was a puzzle to astronomers (a million years is a short time for an atmosphere), but maybe has to do with some kind of geologic activity releasing trapped ices. I’d love to know if you have any corrections to this.

    1. I did simplify a bit, but the abundance of methane vs. carbon dioxide is mainly set by the pressure and temperature profile in the protosolar nebula (and of the protosaturnian nebula, in the case of Titan). I study orbital dynamics, not cosmochemistry, so I must admit that this topic is somewhat beyond my comfort zone, but I try to keep up with the latest in Titan knowledge. Basically, given a reasonable guess as to what the temperature and pressure is in a nebula, as well as the abundance of elements (estimated by assuming that the nebula was composed of the same relative abundances as the Sun) you can work out the equilibrium condensation sequence of various molecular compounds as a function of time and distance from the Sun.

      There is still a big mystery regarding the present abundance of methane on Titan. At the current rate of methane destruction on Titan, the atmosphere should “dry out” within a few tens of millions of years, which is very soon compared to the 4.6 billion year age of the solar system. So either we are incredibly lucky to be witnessing the last gasp of titanian methane, or there is some underground reservoir of primordial methane that is slowly leaking out onto the surface. People have been proposing cryovolcanism (volcanoes that erupt water rather than molten rock) as a possible mechanism for bringing methane up from deep underground somewhere. However, a recent talk I saw by someone who knows his icy satellites suggests that the evidence for volcanoes on Titan is pretty shaky, and that Titan may turn out to be “Callisto with weather” (Callisto is the mostly undifferentiated, heavily cratered and geologically dead outermost big satellite of Jupiter). Titan is a fascinating place with no shortage of mysteries.

  10. The oil isn’t being generated at the rate of millions of barrels a day, so we’re going to run out whether it’s biotic or abiotic — then we won’t be able to post blog comments, exercise our fair use rights to digital media, power our iPads or Kindles, or feed ourselves…

  11. If, in fact, oil is abiogenic as Gold suggests (and I highly recommend Deep Hot Biosphere) and it *IS* being replenished at a rate which does not exceed its withdrawal, that would suggest that the scarcity of the substance is a deception and that the high prices are largely artificial. That would be worth noting, would it not? If this is indeed known, and is being withheld, like research on the harmful effects of tobacco, for example, then who would be the likeliest suspects in such a scheme? Further, is this far-fetched? Much of the data around petroleum extraction, processing, and location is tightly and effectively controlled. Would it be that difficult to keep this information hidden?

    This article recently mentioned that a new book from the New York Academy of Sciences asserts that one million people were killed world-wide by the Chernobyl meltdown.


    The article also mentions that this is common information in Eastern Europe and the former Soviet Union, but the research has not been given notice in the West. If one million people can be killed by such a high profile event and the data ignored or intentionally hidden, is it also not possible for something like this abiogenic information to remain ignored or intentionally hidden?

    We in the West, but Americans in particular, simply cannot and will not believe that in a society as awash in information as ours that we could miss ANYTHING. Yet, we don’t consider that much of the information is superfluous or is in fact disinformation. There’s a lot of info out there, but how much of it is valid?

    I will simply leave it at this… I am of the opinion that virtually nothing the public “knows” about petroleum is accurate and that is by design.

    Most of the discussions we have about petroleum are based on faulty data. Much like our discussions about food, where most of the packaging and marketing do not in any way match the results that we see manifested in our own bodies.

    1. Lev Davidovich, the tobacco industry never managed to prevent people from finding out that tobacco was bad for you. At no point did they succeed in suppressing any research other than their own internal research, and even that leaked very badly (from their point of view).

      What they did succeed in doing was saturating print and voice media with contrarian propaganda. This method is how pollution denialism works today; re-label a pollution crisis as “global warming” (merely one symptom of a particular type of pollution, and not the most worrisome one) and then generate a fake controversy about it. Eventually you can get your opponents to stop talking about pollution and start talking about global warming, and then you win.

      The difference between this strategy and suppressing real information is important; if you successfully suppress data, nobody can find out for themselves what is going on. This never happened with tobacco or pollution- thinking people have always been able to investigate for themselves and reach verifiable correct conclusions.

      I personally investigated the Mauna Loa and ice core data over 15 years ago. It was not particularly hard to figure out who was lying and how. The atmosphere is being converted to an unhealthy soup; carbon pollution and the attendant albedo modification is real. But I don’t talk about “global warming” because that just puts the battle in the field of Big Oil’s choosing. I say “air pollution” or “public health crisis” or “industrial disease” instead, because I don’t care to argue about one individual symptom, I care about solving the problem.

      The data’s out there. You can get access to it. You don’t have to accept what I say, or what people who want to sell you a new car say.

  12. Really nice that the number of people on earth today depend on for survival this as an energy (and technology base) source…but nobody knows where it comes from (besides the obvious) or how fast it’ll run out.

  13. Professor Challenger answered this one decades ago:

    “Then came the geyser. It was an enormous spout of vile treacly substance of the consistence of tar, which shot up into the air to a height which has been computed at two thousand feet. An inquisitive aeroplane, which had been hovering over the scene, was picked off as by an Archie and made a forced landing, man and machine buried in filth. This horrible stuff, which had a most penetrating and nauseous odour, may have represented the life blood of the planet, or it may be, as Professor Driesinger and the Berlin School maintain, that it is a protective secretion, analogous to that of the skunk…”

  14. If petroleum is created from decomposed surface plants then burning it just returns to the atmosphere carbon dioxide which once came from it thereby restoring the original balance. If petroleum isn’t from decomposed surface plants then burning it release a lot of carbon dioxide into the atmosphere that the surface biosphere never was adapted to.

  15. “The idea is that, unlike the rest of the biologic material, lipids don’t get gobbled up by bacteria, instead falling out to the bottom of the ocean, where they’re covered by millions of years of sediment and eventually become oil.”

    The problem with this idea is that lipids are less dense than water, especially salt water, and will float on the surface of the ocean.

  16. “The suggestion that petroleum might have arisen from some transformation of squashed fish or biological detritus is surely the silliest notion to have been entertained by substantial numbers of persons over an extended period of time.”
    — Fred Hoyle 1982 —

  17. I believe the earth uses the oil to burn its core and in removing it from the earth can harm us in ways we can’t imagine … could this be possible?

  18. I don’t think scientist really know where oil comes from.I sense this because of the fact that Saturn’s moon titan is full of oil and natural gas, so by scientist explanation of where oil and gas comes from titan must have been under water where plankton and plant material gathered to get to 65 to 100 degrees then started to form oil and natural gas yeah right. I think oil and the natural gas was trapped here at the beginning of creation just like on titan.

  19. Actually Anon, It is produced continuously by the melting plates below us. It has nothing to do with plankton, dead dinosaurs, cellulose or any other sophomoric explanation to date. Coal, tar and oil are all one in the same. ( take a mass spec of each and see for yourself ) The necessary elements, heat and pressures are all down there and the carbon, hydrogen, steam and everything else necessary to produce oil and gas are constantly being produced, released and re absorbed when the plates melt and re form. Burn any rock……ANY….and do a mass spec on the findings. imagine that. It’s all there. Don’t expect scientists and educators to be on board. We have been drilling oil for just over 150 years and the origin of oil has changes 3 times to date. By the way, a theoretical mathematician was the first to dispute the scientific findings on the origins of oil. Only a very small percentage of any living thing can be made into oil after breakdown and he calculated that to achieve a trillion barrels of oil ( which is what we have used world wide to date ) the numbers of plankton, dead dinosaurs, cellulose etc. was astronomical considering the basic body make up consisted of 60 to 90% water and other inert elements.

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