rethinking petroleum a little too hard, redux

April 20, 2011

Uh oh. Just when you thought that we were once again safe from the abiogenic oil theory I had to debunk last year, there’s now some theoretical chemistry which says that maybe, possibly, methane could form chains of hydrocarbons about 70 miles down, at pressures past 50,000 atmospheres and temperatures of 1,227 °C or greater. And here’s the funny thing. This is just a simulation of a more or less pristine environment where one could decompose pure methane in just the right conditions and the authors don’t claim that they know where deposits of abiogenic hydrocarbons would be. In fact, they don’t even make the claim that such deposits even exist since the brief paper itself is basically a hypothesis-fishing expedition, designed to see if there’s any way that one could get hydrocarbons down in the Earth’s mantle. The answer isn’t a positive, but more of a maybe if all the conditions align and the simulation hasn’t forgotten to include something. But of course, leave it to a headline on Popular Science to claim that there’s evidence of abiogenic oil and summoning the abiotic troll brigade, which insists that there’s some grand conspiracy by OPEC or environmentalists to bury the idea.

Since my previous post on abiogenic oil, not a thing has changed. No abiogenic deposits have been found in places where we expect them to be, and nothing has overturned the many years of study showing that typical barrels of petroleum we recover today come from anything other than the decay of marine life under pressure and heat for hundreds of thousands of years. That’s not what those who cling to the abiogenic hypothesis are interested in hearing, however. They don’t want to run out of oil. They want to keep things as they are and they want to make sure that OPEC is given its rightful share of blame for conspiring to limit the supplies of oil and hold the global economy hostage. If there’s no limit to the amount of oil in the ground, there’s no need for any changes or a global resource repositioning. There’s no need to spend money on new generations of cars or new methods of generating electricity. There’s no need to be involved in the Middle East and make unsavory, ethically questionable alliances for oil which have directed the ire of tens of millions to the U.S. and Europe in the last several decades. And when oil is everywhere, as long as you’re willing to drill deep enough to get it, it makes no sense to worry about all sorts of complicated environmental and political problems.

Unfortunately it doesn’t work that way because what would be convenient and soothing for us isn’t necessarily the way things are in nature. Without a single abiotic deposit of oil, which is found to contain no indication of ever having been keragen, this simulation is actually the strongest piece of evidence for the idea of abiogenic petroleum. And it’s really not much, placing the possible abiogenic hydrocarbons in a model of what might be happening in the outer mantle. Even if the scientists are right, the oil in question is pretty much out of reach to all of our technology since it apparently doesn’t bubble up and pool into deposits just a few miles down and in range of our drills. If the deepest hole ever dug is just a smidge over 7.6 miles, how do we safely drill down to ten times that depth, and even more importantly, how do we know where to even drill? How do we probe for a deposit of hydrocarbons in the mantle, where the insanely high temperatures are more than likely to melt any drilling rig we use? Of what possible use will this abiogenic oil be if we can’t find it? Which brings us back to the original point. If there’s plentiful oil being formed from the planet’s mantle, where is it? Why is all the oil we recover now organic in origin? And why did the predictions of abiogenic oil advocates fail to discover any new and unusual deposits while oil companies have reliably found oil with traditional methods?

And the funny thing is that a good deal of proponents for abiogenic petroleum also happen to deride the study of global warming as a scam at worst, or nothing more than computers models which are subject to errors if the data they’re fed is either fudged or incomplete. Will they embrace this computer model out of confirmation bias and insist that despite being a rather straightforward, let’s-just-see-what-happens calculations which so often turn out to be just a blip on the radar which vanishes when a little more scrutiny is applied, it’s actually a very solid model, solid enough to prove that science is on their side? And if that’s’s true, how do we explain all the other studies into the origins of petroleum, studies in which the abiogenic idea was discarded because it failed to match the data being collected? Would they go the manufactroversy route or say the petroleum could be both organic and inorganic? I guess only time will tell. Really, though, discovering paradigm-shifting things is very difficult and they have to come with a lot of proof. A simulation which doesn’t say a whole hell of a lot on where or how we could actually confirm the existence of petroleum in the mantle doesn’t even come close to making a strong case for abiogenic oil and changing the way we have to think about fossil fuels.

See: Spanu, L., Donadio, D., Hohl, D., Schwegler, E., & Galli, G. (2011). Stability of hydrocarbons at deep Earth pressures and temperatures PNAS DOI: 10.1073/pnas.1014804108

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  • Lucilia Cuprina

    1) Petroleum has a very large preponderence of even-carbon numbers from acetate anabolism.
    2) Chiral petroleum compounds are resolved not racemic.
    3) C-12/C-13 natural abundance variations indicate metabolic enrichment.
    4) Synthetic hydrocarbon processes such as SASOL do not produce outputs mistakeable for petroleum.
    5) Bottom line: Petroleum is a biological product.

    50,000 atmospheres and temperatures of 1,227 °C
    No hydrocarbon exists anywhere near stated condtions on the carbon phase diagram.

  • Dar Norris

    The History Channel has a good documentary called Crude that explains very well the roll of phytoplankton in the making of petroleum.

  • Davide

    To Lucilla: according to the phase diagram no diamond exists at ambient pressure/temperature… uh oh… what’s that on your finger?

    To the blogger: all very well written and true.

  • Tar Baby

    Dunno, SASOL makes long chain and light hydrocarbons, and oxygenates using what is essentially the abiogenic synthesis. Doesn’t sound too implausible to me.