Does oil extraction leave a cavity?

13 February 2011



Hi Chris,
Thank you for your interesting podcast!
My question is, when people pump billions of gallons of fossil fuels out of the earth, does the huge empty hole cause the earth's crust to become unstable and possibly collapse? Does the fossil fuel replenish? I always wondered about this.


Chris - That's a really good question and it's one that actually, we've also had from Ady Yates who said "what do we replace pumped-out oil and gas with?"

I guess I can probably help both of you in one go here. A few years back when I first started doing all this, I thought oil existed underground in these big open caverns, almost like a coal seam - and when you take the coal away you're left with a big cave. But oil's different and, in fact, the best analogy I can think of to explain what it's really like is to imagine sticking a straw into a wet sponge and sucking water out, because that's essentially what the conditions are like underground.

When the oil was formed, it was lots of marine creatures and other organic matter; this got compacted on the sea floor below layers of sediment and the huge pressure heated everything up and cooked all these dead creatures into the soup which became the crude oil that we extract today. But that means that what that material is trapped inside is a porous rock, and I have to acknowledge on our forum,, we had an answer to a similar question a couple of years ago which a geologist on the forum, JimBob, gave a very elegant answer to.

He points out that if you look at the rock that an oil well is drilling into, the porosity of that rock, in other words, the proportion of holes, is about 13%. So in other words, if you take the cross-sectional area that's holes as a whole proportion of the cross-sectional area of the piece of rock, about 13% is just empty space in the rock; and that empty space is filled with the oil. Now, he also says that that is about the same open porosity as concrete.

So, in other words, when you take the oil away, you're left with something which is equivalently strong already to concrete. So you're not leaving a big space. You're just taking the oil out from between all these little holes which are, to a certain extent, in continuity.

But then the next point to bear in mind is that this oil and gas that's underground is under extremely high pressure and that means that as you take the oil or gas away, largely under its own pressure, then other things will move in to displace it. And therefore, some water will move in from the adjacent rock and will also take up some of the space that's been vacated. In fact, when people call a well spent, in other words, they say that an oil well has become empty, actually, the amount of oil that's left behind can be as much as 90%, because the oil is very hard to get out.

To come back to Ady's question, what do we replace it with, well sometimes, you can help to get the oil out by pumping something else into the porous rock such as water to help the oil be pushed up to the surface because it floats on the water. The Norwegians have also got a technique where they pump steam in underground and the steam, being hot, can make the oil become runnier, so it's more likely to consolidate - join together - into big blobs of oil which are easier to get out.

And also, as Dave pointed out earlier when we were discussing this, sometimes they also put surfactants, things like washing up liquid, down underground and that helps the oil to have a lower surface tension so it can flow out of all these little holes more easily.

So, the bottom line is, you're sticking a straw into a sponge; the porosity of that sponge is equivalent to concrete so it's still very tough rock underground; therefore, you don't get left with a great big gaping hole, and therefore there are probably few seismic consequences as a result.


Our well was pumping oil and then the tubing had a suction on it, keeping to fluid from being pumped

Can they be filled with garbage to offset land fills?

People are experimenting with using the geology to sequester CO2 and offset the warming effects produced by burning the oil and gas that had been in the well originally.

Do you think we can effectively pump enough fresh water into the earth where we have drilled oil helping to force out the remaining oil while helping to lower the rising sea level. We pump fresh water into the earth and pump sea water into volcanoes this will help to replace fresh water for rain by way of steam. Also we must find a way to transport water to desert regions of the world.

Are there not cavities in the earth’s crust that via hi tech drilling capability and gravity could serve as reservoirs for excess surface water brought about by periodic flooding?

I was thinking more along the lines that the fossil-fuel layer around the globe is healing the globe
nother words it's the fuel for the engine
Maybe that's what happened on Mars
At the rate we're going the other 90% will be gone I'm a short time
I can't help but think that drilling all these holes in the planet is good for it
I mean we've been drilling for oil for how many years now over a hundred
And I think we have a few more cars now

Forget about the profit and focus on longevity

was this question answered by somebody that works in the petroleum industry? So given that answer tell me how that applies to the Deepwater Horizon catastrophe? So was the Earth squeezing the sponge? Yes at least cavities in the Earth and these cavities and different places are under incredible pressure. The oil in the earth mantels exist In Pockets that are under incredible pressure the reason that they're under pressure is from the weight of our oceans and primarily gravity. What drilling companies do is they locate these veins of oil if you will and they tap into them and extract the oil out under pressure and vacuum . Chris think about it like this these oil cavities in the Earth's mantle let's just say that there quarts of oil in this court of oil is existing in the Earth's mantle and it's not always in rock it's under many different conditions in the mantle now to simplify the question what you're doing is you're basically drilling into the side of that quart of oil that quart of oil is buried with rocks is sediment with these items pressing down upon it but it can't escape its got nowhere to go it's a pocket so it's completely surrounded with all this heavy dense matter all the way around it putting pressure on it. so now what you're going to do is you're going to drill sure all of these layers of rock and sediment in tap into that quart of oil now once the oil has a way to escape it's going to. which is exactly what we saw with the Deepwater Horizon accident all of the weight of the ocean putting force on the mantles was squeezing that stuff out at alarming rates. Yes at least cavities in the Earth you can't take something away from something and not have there be something missing. stating that we're sucking it out of a sponge is hilarious. So what happens when you suck all of the water out of a sponge ? You end up with this little tiny dried up sponge. So did it have any effect on the sponge yes the size of the sponge shrunk dramatically. and yes this is having an effect on the earth and it's very simple to connect the dots like the sinkholes that are appearing randomly all over the place like the disappearing lakes in ocean water that's Vanishing. like the increase in earthquakes that are happening globally. See you can only do this for so long and Earth's gravity or pressure if you will is going to fill in all of these boys because gravity is what keeps the planet all compressed into a round ball just like water always finds its lowest point of equilibrium that's what's going on. But nobody in oil will tell about the no negative effects of drilling for it the long term use of it the problems known problems that presents that were already experiencing because on this planet if it makes you rich who cares. When money is your master morals are your nemesis. I'm shocked that that was actually a scientifically induced answer. There seems to be some discrepancy over where the fossil fuels come from as well. So I'm going to guess that all the creatures on the earth and all the dinosaurs all decided to have and Extinction Festival what in the Middle East and I'll gather there for end-of-life celebrations? The last time I checked human bone is made out of calcium and you can bury calcium in the earth is it's a mineral that exists in the Earth and it will take calcium forever. I wasn't aware of the fact that calcium gets converted into oil it's some point. The dinosaurs are a nice story though. When are we going to stop lying to ourselves and lying to others and believing some of these absolutely ridiculous fables and fictitious realities. It's some point we have to stop making it up as we go along. if you would like to make correlations between petroleum and coal and how they were formed it's easiest to do that by looking at humic acid and lignite coal I think there's a similarity taking place there is there both the decomposition organic materials such as dead plant matter like massive forests that were buried beneath the earth's mantels in a cataclysmic Collision of two entities are Earth and something else possibly another planet or a or a giant meteor. Look at the planet on Google Earth and look at all of its fault lines in the Ring of Fire and then think about a hard ball like a baseball hard ball in the way that the skin on the baseball is stretched over the inner windings and stitched when this Collision took place the land we live on a planet Earth was stretched over the outside of something else everything that was broken and turned under or caught between those two in the layers is where petroleum comes from. Mark my words though there will be an incredible price to pay for all of the oil that we have removed from the Earth's mantels it's not if something happens it's when. And we're beginning to see that now.

Hi everyone.
This was mentioned in original article:
- pumping oil out of porous structures
- it’s hard to get oil out
- concrete - like remaining material (allipuding to stability)
- oil under very big pressure

If the oil is under big pressure, why is it then hard to get out? I guess it’s not under big pressure once you find it.. maybe like a bottle of champagne.
Concerete porosity is not convincing either. I cannot imagine anything being pumped out of concrete.
If we pump 39 billions of oil per year that, simplistically put means gigantic 5.5mio cubic meter hole each year.. that has to be seen somewhere?
Maybe those holes will save the world from ocean flooding because of glacier melting .. so pump more, pump more! :-)

I think the reason we have to buy bottled water is a direct result of poor human stewardship, and greed is the main driver you know liquid gold that is. We bring products to the earths surface eventually disregard and dump into land fills which eventually leach toxins back into the earth and have a direct impact by entering the water table that was once pure and clean my theory I'm not a scientist.

I live in Slovenia and we can buy bittled water.
But at the same time we have clean water in pipes and our wells are protected by law as common good. We should defend it by all means.. hopefully we won’t have to.

Perhaps we need to stop measuring the minutia if specifically whether the earth is de-stabilized ny extraction, or whether the burning of the oil is worse. Intuition and your heart will tell you that aggressive, excessive and ungrateful plundering and polluting the earth is very much not a good thing. Secondly, that half if it is unnecessary vecause it is to service levels of luxury that aren’t needed and do not contribute to happiness and survival. We are wasting time debatingbthese points when its all obviously wrong. We need to voluntarily undertake austarity measures - especially the rich/“one percent”, and distribute those benefits to those who are suffering. The rich shouldn’t be in control, they have a conflict of interest and (erroneously) believe they are shielded from the adverse effects of overindulgence and avwidening gap between haves and have nots.

In my opinion the "elegant" description of the above explanation is not quite convincing. It is not possible to trespass a "porous" material like a solid porous concrete with a "strou" what kind of strou could be able to do that?

Oil it does the same for a engine; now tell the people the truth and this future earth isn't gonna last. More headaches have been diagnose because of the gases coming out the oil fields. If u take helium from a balloon you want stay afloat and if u keep taking oil out the earth it will be lava in the sea lava on land, time zones will go counter clockwise and fire, drowning, and famine will be the end of living on earth. And this is what the bible said to men will run to the stars and they will try to live under ground and even the sea but theirs no hiding place..

What you have written is absolutely wrong and totally misguided. And what the Bible says has got nothing to do with anything.

Oil exists in a tiny proportion of the Earth's crust and is largely statically confined within geological formations where it remains for millions of years until we - or some other event - releases it. It has no role in cooling the planet except insomuch that the sequestered carbon is not contributing to global warming.

The answer supplied above is accurate.

How many years until all the oil runs out

Our direction is 2) fold
1. Immediately find ways to reduce the need for petroleum products.
Photo electric generation and others .
Reduce consumption with electrical transportation of small packages
2. Increase solid state and lithium battery power.

when oil is extracted from the earth, this remove coolant from the core of the earth. what is replace to counteract this. A vehicle engine will not stay cool if it does not have engine oil.

I was thinking the exact thing

No, oil is not a geological coolant and lubricant like it is in a car engine. Nor is oil in the Earth's core; oil forms close to the surface of the Earth's crust and is the remnants of marine biomass transformed over millions of years by low-level heat and high pressure. 

Oil acts as lubricant/cooling in a car engine by coating moving parts and reducing friction, which in turns lowers the heat generated by friction. Where are the moving parts in the earth?

We are removing the coolant from the earth but the big oil people don’t care about that as long as they make that dollar! I am a 56 year old grandmother and I have thought about this for years! What kind of fate are we dooming our children,grandchildren and their children to!!!

I respectfully refer you to the answer above - "No, oil is not a geological coolant..." -

Just in case you missed it, it says - "oil is NOT a geological coolant." 

Humans are now so technologically advanced, that all aspects of the planet's environment is under threat from our activity.

Not only is oil and gas being extracted wherever it's found, we are polluting the sea and the air we breathe by our industrial processes.

To imply that extraction has little real effect on the planet, is I suspect, an unguarded opinion. One wonders at what point humans will wake-up and realize; that they cannot merely plunder the Earth's resources, without having a destabilising effect on the planet.

The plastic microfibers in the sea, is the result of treating the planet like a sewer. Who cares for the effect it is having? Well nature will re-balance the system. It will struggle on, attempting to contain the worst excesses, of a species that hardly deserves to exist, if it cannot 'Take Care' of this beautiful home.

I absolutely agree. The powerful that are causing the catastrophe, have the same conscience as the ones that know that children are dying for hunger every 20 seconds without knowing that their trillions of dollars are not the consequence.

Wow that was a great explanation in regards to oil extracting.

This has been disputed for many years, however when asked to prove that it does not effect the eco structure, scientists then say that only time will prove that question?

The threat posed by burning oil and the attendant CO2 release is almost certainly far beyond the geological risk of the extraction. 

nice info

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