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PeakOil is You

What Is Crude Oil, How Is It Formed?

General discussions of the systemic, societal and civilisational effects of depletion.

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Re: A differently biotic oil?

Unread postby dissident » Sun 17 Mar 2013, 14:50:42

Keith_McClary wrote:
ian807 wrote:For that matter, if either process was creating oil in significant amounts, we would have lakes of oil on the surface of the land, and giant slicks at sea. Microbes that ate oil would have evolved into sufficient abundance that we wouldn't be able to keep oil or gasoline without bacterial decay.

Doesn't add up, no matter how it's spun.
And wouldn't these microbes have to consume oxygen and output CO2 to get energy from eating oil (just like how we get energy from eating McGrease)? So we would have a CO2 atmosphere by now.


That simply does not follow. The release was slow and over millions of years, which is more than enough time for chemical weathering to remove CO2 when it comes down as carbonic acid via rain.

As for these species eating all our oil that is clearly not the case since there are none of these microbes in the oil we pull up from wells. The microbes cannot migrate through the rock matrix, but oil and natural gas can. These microbes dwell not too deep from the surface or the seabed.

http://www.pbs.org/newshour/rundown/201 ... spill.html
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Re: A differently biotic oil?

Unread postby Keith_McClary » Sun 17 Mar 2013, 23:41:38

dissident wrote:That simply does not follow. The release was slow and over millions of years, which is more than enough time for chemical weathering to remove CO2 when it comes down as carbonic acid via rain.
My point was that if the release was fast enough to contribute significantly to current consumption then there would not be "more than enough time for chemical weathering to remove CO2".
"I could go on, but let’s veer off in another direction instead."

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Re: A differently biotic oil?

Unread postby MD » Mon 18 Mar 2013, 08:13:30

Hydrocarbons are being continuously formed all over the Earth is many ways. That's a truth that is evident.

Those of us here that bitch about the constant burning of peak oil straw men by deniers should try to refrain from burning straw men of their own.

It's the -rate- of hydrocarbon formation that's important, not the -fact- of hydrocarbon formation.

If the planet were creating Hydrocarbons at the rate of consumption we would be swimming in the stuff, literally.

Edit:
Before the inevitable dipstick comes along ranting about the "planet" and "abiotic oil": By "planet" I mean the entire sphere and all of its living ecosystems. Have a nice day!
Stop filling dumpsters, as much as you possibly can, and everything will get better.

Just think it through.
It's not hard to do.
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The formation of oil

Unread postby dashster » Mon 20 Apr 2015, 22:09:14

I saw something somewhere that showed oil formation starting at the mouth of a river. Organic deposits settle on the ocean floor and build up. But it didn't show what takes place between that and oil ending up in Pennsylvania. What happened geologically to get these "mouth of the river" deposits spread all over land or miles underneath the deep ocean floor?
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Re: The formation of oil

Unread postby forbin » Tue 21 Apr 2015, 08:45:06

google is your friend

plenty of articles on how oil is formed

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Re: The formation of oil

Unread postby ROCKMAN » Tue 21 Apr 2015, 09:09:10

As Forbin says: more of such info on the web then you'll ever want to read. But here's a hint: not all oil has come from marine sediments...some came from fresh water deposits in river beds. And places such as PA haven't always been nice dry land. Consider that many of the rocks in the limestone fields in the Rockies were formed from marine deposits. Yes: a time long ago Denver was a nice shallow sea rather similar to the Bahamas today.
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Re: The formation of oil

Unread postby Synapsid » Tue 21 Apr 2015, 14:20:49

dashter,

To add a bit to what forbin and ROCKMAN say:

Pennsylvania's oil formed from organics in river sediment (mostly sands) laid down in the shallow sea that covered much of what is now central North America on the order of 350 million years ago. The rivers flowed from mountains to the east, roughly where the Appalachians are now; the sandstones are red and can be seen in southern New York state and other parts of back East. (Rocks of the same age and type can be seen in much of western and northern Great Britain, where the stuff is called the Old Red Sandstone. The rivers carrying the sand were flowing down the east side of the same mountains; the Atlantic didn't begin to open until 150 million years later.)
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Re: The formation of oil

Unread postby sparky » Tue 21 Apr 2015, 15:27:10

.
The arctic oil was formed when the arctic sea was pretty much closed and saw yearly bloom of floating vegetation
before the ice started to appear .
Geology is reading God's book in His own language and His own time
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Re: The formation of oil

Unread postby dashster » Tue 21 Apr 2015, 21:37:01

forbin wrote:google is your friend

plenty of articles on how oil is formed

Forbin


As I stated in my original post I am not looking to read a few general statements about "oil formation". You can find plenty references to organic matter falling to the bottom of the ocean and then being covered up by other sediment. But they don't take it all the way to the end. We don't drill for oil only on the ocean floor. In fact, we didn't drill for it on the ocean floor until modern times. A poster here and one site does mention rivers and swamps, but normally they only mention the ocean. But even with rivers and swamps, you have the issue of it being buried as deep as it is. I was looking for what happens to the earth to get this organic matter buried so deep.

As an example, if a boy was driving by an Oklahoma oil well with his father and asked - how did the oil get down there?, I think it is an insufficient answer to say "organic deposits from long ago that got covered by other matter and the pressure turned them into oil". But that is what you see "using google".
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Re: The formation of oil

Unread postby Synapsid » Tue 21 Apr 2015, 22:52:04

dashter,

There's more than one way that regions can subside and later rise. In the case of what's now the eastern US back in the times I described above, a previous ocean had closed (it's called Iapetus) and the collision between our continent and what are now Europe and Africa created that mountain range I mentioned, and also produced very large-scale flexure in the middle of the continent that took much of it below sea level. The weight of the sediment being deposited in the margins of the mid-continent sea added to the sinking there so that enough material accumulated to lead to burial temperatures that reached the oil window.

When the Central Atlantic began to open about 200 million years ago the eastern side of the North American plate sagged and the interior flexure relaxed, allowing rocks that had been buried deeply to rise again.
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Re: The formation of oil

Unread postby Pops » Wed 22 Apr 2015, 07:42:35

dashster wrote:We don't drill for oil only on the ocean floor.

You are not listening to the answers to your question.

The earth's crust is dynamic, FFs are organic matter trapped and cooked in the process. A few hundred millions years ago when oil was still swamp muck, you'd not have recognized the neighborhood.
What is mountain top now might have been ocean floor.
What is ocean floor today might have been mountain top.
In fact much of what is ocean floor today was once creamy mantle nougat.

Pictures :)

Image

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If destruction be our lot, we must ourselves be its author and finisher. As a nation of freemen we must live through all time or die by suicide.
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Re: The formation of oil

Unread postby ROCKMAN » Wed 22 Apr 2015, 08:07:46

dashter - And here's a very specific answer to your valid question. The term is geosyncline: an area of the planet that's in a continuous state of subsiding. And one of the greatest hydrocarbon generating geosynclines in right here in the US: it's the northern section of the Gulf of Mexico. How much subsidence? On the La. coast there are wells producing hydrocarbons at depths greater then 3 miles. And the rocks containing those hydrocarbons were deposited in water depths of less than 100'. And in some cases in just a few feet. Today you can find roads in S La and Texas running directly into Gulf waters. Originally they didn't: the subsidence continues today.
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Re: The formation of oil

Unread postby ROCKMAN » Wed 22 Apr 2015, 08:19:16

Also let me point out why the vast majority of the world's oceans have zero hydrocarbon potential. While there might be abundant organic material on the deep ocean floors they also lack the type of rocks needed to create reservoirs. Look at a global map and you'll notice that the big offshore oil/NG trends are along the coastlines of the continents. The continents have eroded over hundreds of millions of years. Those sediments get carried to the oceans (just as the Mississippi River drains N American
and carries sediments to the GOM geosyncline) where they accumulate. The Deep Water GOM exist so far from the shore thanks to turbidites. The turbidite mechanism to transport sediments so far from the continent was only recognized about 50 years ago.
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Re: The formation of oil

Unread postby hvacman » Wed 22 Apr 2015, 10:36:32

Geology is reading God's book in His own language and His own time


:) Quote of the day...

Carl Sagan might have added cosmology to that definition.
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Re: The formation of oil

Unread postby Synapsid » Wed 22 Apr 2015, 16:18:15

ROCKMAN,

Geosyncline! Nobody talks about geosynclines--they are so, so yesterday! Positively pre-plate tectonic.

You're letting your age show, ROCK...wait a minute: I'm older than you are...

Never mind.
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Re: The formation of oil

Unread postby rockdoc123 » Wed 22 Apr 2015, 22:56:40

Just a comment from the organic geochemist in the neighborhood. :-D
It is often difficult to summarize hydrocarbon generation in any basin in a few sentences. There are almost invariably numerous phases of uplift and successive burial. Hydrocarbon generation is a product of not just temperature (i.e. burial depth and geothermal gradient) but also time. As a consequence many basins see numerous phases of maturation, generation and migration of the various source rocks present through it's history.
Beyond that the devil is in the details. Kerogen type is significant in terms of the activation energy necessary to convert to hydrocarbon. As a consequence a Type I kerogen would mature at a different rate under the same boundary conditions as would a Type II or Type III kerogen.
Since the 1980's we have been able to model historical hydrocarbon generation in any given basin based on knowledge of source rock characteristics, burial history (burial and tectonic uplift), geothermal gradients through time. More recently we have been able to integrate all of those models with migration models based on reconstructed structural topography and that now in 3D. It should be no surprise that many of the remaining significant conventional fields have been discovered throughout this period.
The shales, however, have a whole different nuance. They are both the source rock and the seal, migration not playing a role.
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