August 21, 2012

Abiogenic petroleum origin

There is a very large body of evidence that oil is continuously being produced deep in the Earth and that it percolates up through faults and collects in pools. The idea that oil was produced from 'dead dinosaurs' or plant material is becoming more and more laughable. Coal is definitely produced from plant material but the chemistry between oil and coal is very different. This came up on an alt.energy email forum and someone posted the link to this fascinating article in Offshore Magazine:
MIDDLE EAST GEOLOGY Why the Middle East fields may produce oil forever
The topography of the Middle East, as it exists today, is the result of a geodynamic system reflected in the creation of subduction zones in Oman, along the Persian/Arabian Gulf area, along the Syrian-Turkish borders, and along the eastern shore of the Mediterranean Sea.

This system is also reflected in rift creation leading to the opening of the Red Sea, the Gulf of Suez, the Gulf of Aqaba, northward to southern Turkey, and between Syria and Jordan. The subduction and rifting are caused by the counterclockwise movements of the Arabian plate from Miocene to Recent, as evidenced by recent earthquakes.

The location and orientation of hydrocarbon fields appear to be controlled by and related to subduction and rifting activities. The formation of hydrocarbons are due to the chemical processes which take place, even today, within the subduction/rift zones, and deep into the basement.

The carbon and hydrogen, necessary for the formation of hydrocarbons, can originate from organic compounds, located in subducted sedimentary rocks, and from the dissociation of carbonates (CaCO3 ), and the reduction of carbon dioxide (CO2 ) and water (H2O) that seeps into subduction zones, or deep into rifts and fractures.

Furthermore, CO2 can be released from cracked olivine and pyroxene in lithospheric and basaltic rocks. The reduction of CO2 to carbon (C), and H20 to hydrogen (H2) is probably catalyzed by oxidizing ferrous iron (Fe+2 ) present in mafic minerals to ferric iron (Fe+3 ). The combination of C and H2, at 300-500�C, has formed paraffinic and naphthenic compounds (both present in the oils of the Middle East).

The continuous formation of hydrocarbons by this process, and the field locations along, near, or above subduction/rift zones, would account for the continuous increase in oil reserves, would explain why hydrocarbons are found close to those zones, and why the reserves are modest in Syria, Turkey, and Oman, relative to the huge oil reserves found in the countries along the Gulf.
Lots of links to source material. This was written in 1995 so it predates a lot of the really deep water finds (Brazil, Indonesia, etc...) Finds that never were exposed to the surface and therefore had no plant formation. Posted by DaveH at August 21, 2012 1:23 PM
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