55
$\begingroup$

We all know that oil is an essentially nonrenewable resource over human time scales. However, I am currently working on an activity for high schoolers that teaches them to predict how long humans can continue extracting oil before running out (and what a sustainable rate of extraction would be).

To that end, does anyone know roughly how much oil is created each year, (in the entire crust, no matter how inaccessible)?

Improve this question
$\endgroup$
5
  • $\begingroup$ All fossil fuels or just resources used to create gasoline (petro)? $\endgroup$
    – Neo
    Commented Apr 26, 2014 at 5:35
  • 1
    $\begingroup$ For the original purposes of my question, just oil that is destined for refining. However, the question of total fossil fuel production is also interesting, since there is a certain degree of fungibility when we talk about electricity generation and switching between natural gas and gasoline for cars. $\endgroup$
    – Kupyn
    Commented Apr 26, 2014 at 6:29
  • 6
    $\begingroup$ Good question. Besides liquid hydrocarbons, there's also a lot of methane generation in the subsurface (from various sources, not just 'fossil' ones), that it would be interesting to quantify. $\endgroup$
    – Matt Hall
    Commented Apr 26, 2014 at 13:04
  • 1
    $\begingroup$ In this case, replenishment rate is pretty much irrelevant to the limit of sustainability: the limiter is in the sinks, not the sources. $\endgroup$
    – 410 gone
    Commented Apr 28, 2014 at 13:10
  • $\begingroup$ I heard once from a mycologist friend that the production of oil from algal mats that produced much of today's oil was due to the lack of fungi at that time in earth's history, I assume meaning that today's fungi would break down that organic matter before it could become oil (or in some way that doesn't lend itself to oil formation). I'm way out of my area of expertise here, so I quite possibly misunderstood her, or I could be missing something obvious. $\endgroup$
    – msulis
    Commented Jan 24, 2018 at 0:01

3 Answers 3

Reset to default
22
$\begingroup$

I can't provide numbers, but a hopefully reasonable outline for your own calculations:

All that is required for oil to form is a source-rock brought to the right depths in a sedimentary basin and the oil migrating into a host-rock. If it is economically profitable (See Footnote) it goes into the global reserve calculation. (Petroleum Sedimentology Winfried Zimmerle, H. Zimmerle)

Oil window

All you need to calculate the oil production is an estimate of the volume of host-rock that is currently under those conditions in sedimentary basins around the world.

Sedimentary basins

As you can see there is a staggering area of Earth covered by sedimentary basins, and all those basins have a certain volume under oil generating conditions.

You will probably also need a rough estimate of how much oil can come out of an average source-rock, and how much will be trapped in economically profitable host-rock traps. Maybe a factor that takes into account the basin type, would also help to improve the calculation (Compressional basins would have a lot of antiform traps, while extensional basins have tilted bed traps).

I have the feeling that the total oil inventory of Earth is probably a Logistic function. Once all the oil traps are filled all the excessive oil is lost to migration or too much heat. Empty traps would mean that oil would find a place to accumulate. So it might even be a self-stabilizing system (but not in human-time-scale, but let's see how long we last).

I think that this would yield an order-of-magnitude answer. It is possible that somebody already made these calculations and I would love to see the numbers.

Footnote: Oil, like all resources, follows mining economics. If you earn money, you mine, if you loose money, you leave. This also means that if more money can be earned, there are also more deposits worth the effort. Calculations with today's reserves are almost useless, because they can't predict what people will be willing to pay for oil in the future. Even if mining becomes unprofitable, we might produce synthetic oil, just because it is a convenient chemical (energy stored in relation to mass, diffusivity, and danger). We kind of already have that with rapeseed oil, which sadly can get a better price to power rich countries cars, than feed poor countries people.

Improve this answer
$\endgroup$
10
  • $\begingroup$ +1 Nice answer, though appears I have misunderstood your theory that price changes correlate oil reserves, since it appears to be flawed given a review of Inflation Adjusted Oil Prices from 1946 to 2012 appears to show no fixed correlation to reserve estimates. $\endgroup$
    – blunders
    Commented Apr 27, 2014 at 22:11
  • $\begingroup$ @blunders - Look at this chart. The OPEC reserves haven't changed in the last 20 years. Increasing reserve estimates would make oil cheaper, lowering reserves would make it more expensive. And on a yearly basis the slight increase of oil prizes makes more effort profitable and keeps the reserves stable: scotterb.files.wordpress.com/2010/12/opec.png $\endgroup$
    – tobias47n9e
    Commented Apr 27, 2014 at 22:19
  • $\begingroup$ Then you agree that your analysis of how much is in the ground is meaningless, since what might be found is meaningless in terms of what is available; meaning the reserve will stay the same, it's the price that will move. If so, doesn't matter how much is in the ground, we will never run out of oil, and Peak oil in the end will be about a declining use of oil, as I stated; though likely could have been more clear, as you were about mining economics, which is why I upvoted your answer. Also, worth noting that the oil price changes appear to be driven by speculation, not demand with the markets. $\endgroup$
    – blunders
    Commented Apr 27, 2014 at 22:30
  • 3
    $\begingroup$ I think economics were not part of the question. $\endgroup$
    – gerrit ♦
    Commented Apr 27, 2014 at 23:17
  • 1
    $\begingroup$ Reserves might "stay the same" in terms of their total monetary value. But they are undeniably decreasing in total mass (if you're counting total oil in the crust, as per the question, as opposed to known reserves). $\endgroup$
    – naught101
    Commented Apr 28, 2014 at 6:51
10
$\begingroup$

According to this University of Wisconsin reference http://whyfiles.org/100oil/2a.html

12.5% of oil and gas is from organisms that lived 5 to 34 million years ago.

So if we take an estimate for the total oil in place before human extraction of 4 trillion barrels, this would be 500 billon barrels.

So a crude estimate might be 500 billion barrels per 30 million years or 17,000 barrels per year.

Improve this answer
$\endgroup$
4
  • 1
    $\begingroup$ The calculation isn't clear. How is the amount extracted related to the pre-historic accumulation rate? $\endgroup$
    – David LeBauer
    Commented Jul 3, 2015 at 13:29
  • 1
    $\begingroup$ @David, the amount extracted is unrelated. My calculation multiplies the 12.5% value by the total amount of oil in existence prior to any extraction. $\endgroup$
    – DavePhD
    Commented Jul 3, 2015 at 23:17
  • $\begingroup$ Let me guess the 4 trillion barrels are proven (or recoverable) reservoirs only. To use this type of balance you need to add the amount of oil that has not been discovered or that is not recoverable. These rise the figure by an order of magnitude $\endgroup$
    – DrGC
    Commented Jan 20, 2017 at 20:31
  • 1
    $\begingroup$ The big trick is it is consistent, it is affected by climatic conditions and geological trends at the time it is buried, that's why some periods show almost no production and others a great deal. $\endgroup$
    – John
    Commented Jan 21, 2017 at 1:58
4
$\begingroup$

Around 80,000 barrels per year?

One way to have a rough estimate is to assume that the rate of oil formation has not changed since the Mesozoic. The vast majority of oil reservoirs formed during the last 250 million years. All we need to know is the total oil formed in that period:

By 2009 we had consumed CB2009 = 1.0e11 to 1.35e11 oil tonnes. [https://phys.org/news/2009-05-oil.html]

The proven (90% chance of recoverability) reserves at that time were PR2009 = 2.2e11 tonnes. [http://www.forbes.com/sites/judeclemente/2015/06/25/how-much-oil-does-the-world-have-left/#1688f3955dc5]

The unproven (known reservoirs that are non profitable under present economic and technological conditions), may account for 4 times the proven reserves. Let's label that factor as UPFC=4.

But the biggest uncertainty comes from estimating the unknown oil reserves (reservoirs that are not yet known). Estimates are disperse, not even providing a precise order of magnitude. Depends, for example, on how you evaluate this figure:

oil discoveries

If you assume that we are around half way of discovering all oil reservoirs accumulated on the Earth's sedimentary basins, then you just have to divide by the 250e6 years they took to form.

The average rate of oil formation is therefore:
(CB2009 + PR2009) * UPFC * 2 / 250e6 = 11,200 tonnes/year = 80,000 barrels/year

Note that this is the average Mesozoic+Cenozoic oil formation rate minus the average oil degradation rate (oil is also lost after its formation through different natural processes).

Improve this answer
$\endgroup$
5
  • 3
    $\begingroup$ Related answer at earthscience.stackexchange.com/questions/2503/…, quotes Klemme and Ulmishek: "Six stratigraphic intervals, representing one-third of Phanerozoic time, contain petroleum source rocks that have provided more than 90% of the world's discovered original reserves of oil and gas (in barrels of oil equivalent). " That is, most of the processes that created our current oil supply ended more than 100 million years ago. $\endgroup$
    – jeffronicus
    Commented Jan 27, 2017 at 0:48
  • $\begingroup$ @jeffronicus I don't see how you arrived art your conclusion based upon what you quoted. Notice that the oligocene+miocene (with 12.5% of reserves) lasted 28 my where the Cretaceous (with 29%) lasted 79 million years. I discount the "middle" qualifier on "Cretaceous" because geologists generally don't definite a "Middle" Cretaceous. $\endgroup$
    – Spencer
    Commented Jan 26, 2018 at 12:26
  • $\begingroup$ How big are the barrels? It would make more sense if you stated your answer in liquid measurement units. (e.g. gallons or liters) $\endgroup$
    – Eevee
    Commented Feb 9, 2018 at 14:41
  • 1
    $\begingroup$ @Imtherealsanic Barrel is a liquid measurement unit. $\endgroup$
    – plannapus
    Commented Feb 9, 2018 at 16:07
  • $\begingroup$ oh, well I'll need to research how much a barrel is. $\endgroup$
    – Eevee
    Commented Feb 9, 2018 at 16:09

Your Answer

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

Not the answer you're looking for? Browse other questions tagged or ask your own question.