Where Does Oil Come From?

Did you know that geologists don't have a decent explanation for where oil comes from? This should make you think twice about all those estimates about how we're running out of the stuff.

Geologists do have a good explanation of where coal comes from - its decayed, buried plant matter.

Unfortunately, most people think this story works for oil too. It doesn't.

Here's a basic description of a little organic chemistry. Plants are mostly made of sugars. Sugars are mostly composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio. When plants decay, those sugars break down into carbon and water (which has the right 2:1 ratio). In a perfect world, no elements are lost in this simple description, and nothing is created that we have trouble explaining. The problem with oil is that it is composed of lots of molecules in a ratio of 1 carbon to 2 hydrogens, with 2 extra hydrogens thrown in at the end (for example, natural gas is mostly 1 carbon and 4 hydrogen, while gasoline is mostly 8 carbons and 18 hydrogens). So, there are two problems with the plants into oil idea. First, where did the oxygen from the plants go? If this is how oil was created, oxygen would be pouring out of the humus. It isn't. Second, where do the two extra hydrogen come from? Hydrogen is the most common element in the Earth, so there are a lot of potential sources. However, hydrogen is always tightly bound up with some other element - so in order to get the extra hydrogen to make oil, there have to be lots chemicals in the Earth's crust that are short hydrogen. There aren't.

An alternative theory that I heard about almost 20 years ago is that either there are huge pools of oil under the crust of the Earth, or alternatively, that something is making oil down there. Like bacteria that like hot oxygen-poor environments. This is called the abiotic theory of oil formation. It was thought up by Russian scientists in the 1950's ... when Russian science was in its heydey.

Tip of the hat to Econopundit and the May 23rd post entitled "Big Oil: It May Be Bigger Than You Think...."

Update: Bruce Bartlett and The Washington Times catch up with voluntaryXchange after 11 months.

Comments

[sonia]

Oil actually comes from decomposed fossils over millions of years

[Dave Tufte]

This is precisely the point - it doesn't come from fossils at all, and it's not straightforward to figure out how it came from other organic material either. Yet many people believe this - myself included up until I was about 25.

Fossils are derived from mineral rich tissues of dead organisms. Through poorly understood processes, some of those minerals are replaced by new ones, some of the original ones are retained, and the organic material in between the minerals may be replaced by mineral and sand-like fills.

What you mean by fossils (I think) is just decaying plant material (which fossilizes poorly). The problem with this theory is the arithmetic problems outlined in my post. In short, for plant decay and metamorphosis to produce oil, there has to be a source of hydrogen in the earth's crust we've missed (which seems unlikely), and a place for all the surplus oxygen produced by such a process to go (if this were coming out of the ground we would have problems with the soil spontaneously combusting in some locations ... and we don't).

The theory that oil comes from plant decay was a good one that served us well for many decades. It is only over the last 3 decades or so that we have become aware that there are microorganisms living in regions of the planet that were thought to be inhospitable (for example, it was considered heretical 20 years ago to think that bacteria caused stomach ulcers). There are sensible reasons to think that those microorganisms may have biological processes that yield oil as their waste. This isn't farfetched - such waste would have the same useful properties as our own, in that it burns readily in the presence of oxygen and a flame to start it out.

Now, this is just a theory. It isn't held to by the majority of geologists. But it has been through the phases where it was labeled crazy, and then speculative, and it is still gaining ground. Check back on this topic in 10-20 years.

[Chuck Simmons]

Dave -- Regarding the arithmetic, we can use 1 sugar (c6o6h12) to create 3 methane and 3 carbon dioxide (just paying attention to the arithmetic and ignoring minor details like energy). Any free oxygen molecules in the earth's surface should rapidly react with other stuff -- silicon, iron, carbon, whatever. So getting rid of the oxygen isn't a problem. And you don't need to supply surplus hydrogen.

[Dave Tufte]

This is correct, but I feel as if you've caught me on a technicality.

You could do the arithmetic this way (or do something like break glucose down into 2 ethanes, 2 carbon dioxides, and an oxygen molecule).

Fundamentally you run into the same problem though: your math suggests we should find lots of carbon dioxide under the ground (or other byproducts), and my initial math suggests that hydrogen has to be added somehow. The bottom line is that converting predominantly carbon-hydrogen-oxygen molecules to primarily carbon-hydrogen (oil) requires some unusual behavior that conversion to carbon and water (coal and ground water) does not.

[chuck simmons]

I didn't make a minor technical correction. You basically said: if we look at the ratios of atoms present in biological molecules and the ratios of atoms present in oil, it's clear that we need to get rid of oxygen and add hydrogen. I pointed out that we could equally well remove carbon instead of adding hydrogen.

While I don't know jack about geology or chemistry, I would tend to agree that it makes sense that it would be difficult for the earth's crust to supply extra hydrogen. However, it appears that it is very easy for the earth to abosrb both carbon and oxygen. (calcium carbonate aka limestone, just one of numerous carbonates, appears to comprise about 4% of the crust and even be associated with oil deposits.)

Also note that both coal and oil are complex mixtures of minerals and molecules. Removing all oxygen and hydrogen from sugar would basically leave you with graphite or diamond. Coal would tend to have a bit of hydrogen still attached to it.

Oil has a variety of different kinds of hydrocarbons. Some are cyclic. It is not at all clear that on average oil has excess hydrogen compared to sugar.

Methane, where you do clearly want a higher hydrogen-carbon ratio than is supplied by sugar, can also clearly be formed abiotically. (Titan has methane, and methane is released in volcanic explosions.)

So, I don't know whether oil forms biotically or abiotically. What I do know is that your line of argument that oil forms abiotically is definitely not a convincing line of argument.

The standard abiotic arguments are easy to find on-line:
http://www.gasresources.net/ThrmcCnstrnts.htm
http://www.gasresources.net/AlkaneGenesis.htm
This discuss the entropy of the reactions involved and hence are a bit stronger of an argument. However, these papers note that pairs of chemical reactions can occur. Thus, I am not convinced that sugar might react in the presence of, say, sulphur to move an oxygen atom from the sugar to the sulphur while releasing heat.

[Dave Tufte]

Agreed.

1) I like your point about carbon, and carbonates.
2) In my defense, I was trying to simplify in implying that coal was pure carbon.
3) The vast majority of what comes out of the ground in crude oil has more hydrogen than carbon.
4) I wasn't claiming that my argument was (terribly) convincing. What I was trying to do was point out that a novice doesn't need to know much about chemistry - only some arithmetic - to see that the biotic theory of oil has some chinks in its armor.

I am glad to see that you are open minded about theories, but unconvinced of the abiotic theory. I am in the same boat.

I am worried that: 1) most people have an opinion about the source of oil, but have no background to debate the point, and 2) reasonable dissent about this is stifled.

[George]

Hi, I am not a member of this forum, but would like to add a different view of the oil thing if I may.... What about the "mexican jumping bean theory ?". If you think for a minute you will see what I mean. It's kinda like the parasite-host concept....just remember the worm that became trapped in it's host.
Not exactly rocket science here...more like an "as above...so below" parable.
Thanks for letting me share this...

[Dave Tufte]

I'm not really sure what the point of this is. Care to elaborate?

[louis miller]

I thought that most people [in the free world that is ] knew the center of the earth was like a large reacator and one of the byproducts is oil

[tugger]

I have been asking for years "where does oil come from." This is the only logical explanation yet; however, I'm still perplexed. Millions and millions of gallons, yet it still comes.
I wonder if volcanos act like the burn off pipes you see when passing refineries?

[sudhir das]

The level of ignorance displayed in this post (and some of the comments) is truly amazing.

A 5 minute google search would have answered most of your questions.

[Dave Tufte]

Uh oh ... troll.

[Jon Sarfati]

The actual source of oil was a world wide flood buried trillions of tons of organic matter. Many layers of sediments were deposited on top in a great cataclysmic event that created the pressures and volumes necessary for oil formation.

[Dave Tufte]

Agreed Jon.

Except, this theory does not explain where the extra hydrogen comes from, or alternatively where the extra oxygen that was mated in the sugars and starches went.

With coal, this is an easy story - the hydrogen and oxygen left together as water. With oil and gas, the math doesn't work without some other factor.