I am aware that it's a bit general a question, and petroleum geology (or petrology ;-)) has never been a field of interest to me. A superficial search using related keywords brings up only economic figures about percentages here and there.

From a geoscience point-of-view is there any chance to give an estimate, however rough it may be, of how much was ever produced in the biospehere (and abiogenic if that plays a role and can be set in number), and how much of that made it into reservoirs ?

I am very well aware that there is a lot of uncertainty, concerning formation processes, mobility in the crust, amount of current storage, past conditions favourable for the formation, etc, but maybe petroleum geology has once thought about it, and knows a rough number.

  • $\begingroup$ Are you asking about all types of oil deposits:porous media, such as sandstone; oil sands such as the Athabasca oil sands in Canada; oil shale? $\endgroup$
    – Fred
    Jun 19, 2020 at 20:05
  • $\begingroup$ @Fred if that can be said with some certainty, then yes, else no problem if the answer is general. I faintly recall, looong ago, that some professor in a basic lecture said something like "only a tiny part of all oil from earth history is stored in crustal reservoires". $\endgroup$
    – user20217
    Jun 19, 2020 at 20:39
  • $\begingroup$ Can't definitively judge the relevance: possible hypothetical constant production of hydrocarbons at hydrothermal vents: science.sciencemag.org/content/319/5863/604. $\endgroup$
    – user20217
    Jun 19, 2020 at 22:55
  • 1
    $\begingroup$ I am in no position for an own judgement on the matter but if the source is Wikipedia it seems to be outdated by the mentioned publication (which is hypothetic in itself as the authors admit). But here's another one: nature.com/articles/ngeo591 All admit that generally petroleum is of biologic origin and abiotic processes, if they exist, have marginal significance. Anyway, I am not siding with noone and can take the "abiogenic" out to avoid action and the question is still there :-) $\endgroup$
    – user20217
    Jun 20, 2020 at 1:21
  • 1
    $\begingroup$ to find an answer to this it might be better to include all carbon that is stored alive and dead and compare it to the CO2 in the atmosphere over earths history,it might be possible to find an max/min value of the amount stored/released even if this has a wide margin of error. $\endgroup$ Jun 20, 2020 at 6:01

1 Answer 1


In its 1995 assessment of total world oil supplies, the U.S. Geological Survey (USGS) estimated that about 3 trillion barrels of recoverable oil originally existed on Earth and that about 710 billion barrels of that amount had been consumed by 1995.

There may be much larger quantities that are not "recoverable", depending on technology and economics.

Also, for example, 914 persistent natural seeps across the Gulf of Mexico collectively discharged about 500,000 barrels of oil per year. If that has been seeping for millions of years, that is a lot of oil that is not in reservoirs.

  • 1
    $\begingroup$ Ok +1 for your efforts, but it's not quite an answer. Those 3 billion are an estimate of what exists today, of what has made it into a crustal reservoire, a part of earth's stratigraphy where it became trapped. But how much has ever formed through earth history so that this part came upon us ? My hypothesis/speculation is that those 3 billions are only a small part (bad news for climate, but that's a different story). $\endgroup$
    – user20217
    Jun 19, 2020 at 23:01
  • 1
    $\begingroup$ We have the 3 trillion recoverable plus the non-recoverable plus all the seepage over history (anything else?). Wikipedia only has numbers for Gulf of Mexico: 600 natural oil seeps that leak between one and five million barrels of oil per year. That alone, over tens of millions of years, would be in the trillions. $\endgroup$ Jun 20, 2020 at 1:19
  • $\begingroup$ And there are very large deposits in methane hydrate on the ocean floors. $\endgroup$ Dec 24, 2020 at 16:16

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.