Q for the Geologists re: oil deposits

[Posteritatis]

I came across a few links of oil deposits/exploration areas here and there over the past few days. Here's an example of one from another DU thread:

http://www.judicialwatch.org/IraqOilMap.pdf


I notice there's a pattern to the deposits in that - instead of being blob-type things here and there they tend to be stretched out, and it's almost like there's a stream of them running southeast (or east and south seperately in the south of the country). It's an arrangement I've seen a lot in maps of other areas - instead of scattered or concentrated blobs-o-oil, it always seems to be stretched out in some kind of pattern like that.

Anyone out there with old-Earth-stuff-fu able to say why the deposits end up that way?

[madeline_con]

1. I'm no scientist, but I'm told....

peteroleum deposits are what's left of ancient (prehistoric) forests. So, it seems reasonable that, like the equatorial rain forests, these would have been distributed in certain environmental regions, and so would be in a stream as you put it.

:shrug:

[XemaSab]

2. Oil deposits frequently occur in geologically folded formations

so they're not really in a "stream," it's more like taking a Hoho and slicing it lengthwise where it looks like all the chocolate is in a linear pattern, when it really started out rolled up. Does that make sense?

ps Don't google hoho.

[gkdmaths]

3. I googled hoho

it wasnt that bad. ;)

From my early geochem studies (though I didnt pursue geochem or, more importantly pertoleum speculation) I remember that oil/coal deposits are largely a product of estuarine environments. In my area (PNW), the reason for oil/coal are catasrophic flooding (specifically tsunami). There's also significant terrain accretion (collection of landmasses by techtonic motion) in my area, but I have no idea of the geology of Iraq.

Ultimately, I think any specific formation is dependent upon the historic topography, land cover and climate of the local region and the conditions being favorable for the development of oil vs. coal vs nothing.

my modestly educated $0.02.

:)

edited for, oh...nothing.

[Posteritatis]

5. I am become clued; thanks, all! (n/t)

[Mistwell]

8. You win...

...the oddest comparison of the day award!

[Fox Mulder]

4. Ooohh...geology question.

I'd answer, but I think XemaSab pretty much got it. :thumbsup:

[scholarsOrAcademics]

6. ball-park estimates of Thomas Gold

I've been trying to get a personal copy of his book The Deep Hot Biomass, from Abe Books and the outfit I ordered from did not come through. There are about 30 used copies available, maybe I will get one from India. He recently died, and I suspect there is no follow up by anyone else. His thesis is that vegetative degeneration is not the primary source, maybe 5%(?). Instead the process starts 100-300 miles underground and percolates through to the surface changing as it progresses upward to the surface. More when I get a personal copy and reread it.

[scholarsOrAcademics]

9. new to me,a new science. geophysics

its difficult to keep up, but the ball-park estimates seems to be what geophysics is about. I've started rereading Deep Hot Biosphere. I'm struck by his comment that respiration by cells,plant and animals, takes only about a tenth of that of a photon. Photosynthesis, plants, of course are into photo conversion. So cells deep in the earth have to tely on chemical energy. Methane oxidized by sulfates, for example.And,the 100 to 300 is kilometers, not miles.

[jfkraus]

7. Geology of oil deposits

Although oil deposits originate from ancient bio-mass, the present day shape of the deposits is largely reflective of the shape of the geologic strata. As noted above, the rocks can be folded and faulted during orogenic events (mountain building). Oil and natural gas want to migrate upwards through permeable rock strata because they are lighter. Oil deposits are the result of the oil getting trapped due to some geologic structure where less permeable rocks overlie the oil preventing it from further migration and causing it to collect. So the oil deposits tend to take the shape of the confining rock strata.