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How is oil formed according to the French Petroleum Institute ?
The Maillard reaction in geochemistry: petroleum, coal and gas
by Eric Lichtfouse
The Maillard reaction is regarded by geochemists as one of the theory explaining the formation of petroleum and coal in sediments. Fossil organic carbon is formed in sediments of lakes and seas by the decomposition of living organisms such as plants, algae and bacteria. 99.99 % of this matter is rapidly degraded into carbon dioxide then recycled to the atmosphere. The remaining matter, though representing a small percentage (0.01%), has been slowly buried over hundreds of millions of years, thus giving rise to huge amounts of fossil carbon. Indeed, the estimated amount of fossil carbon stored on earth is 1016 tons, thus representing ten thousand times the amount of carbon of living organisms!
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The Maillard reaction is occurring readily at the beginning of the decomposition of living organisms in waters and sediments. Intense microbial degradation cuts biopolymers into small molecules such as sugars, phenols, and amino acids. Here it is noteworthy that Louis Camille Maillard in his browning reaction experiments has used very similar laboratory conditions. Similarly, in sediments, small molecules react together to produce a yellow-brown organic network called "humic substances" that becomes a black material called "kerogen" with burial and temperature then yields petroleum. The Maillard reaction thus allows the formation of an organic network that survives millions of years of burial in sediments! Petroleum is formed by the breakdown of kerogen in deep sedimentary rocks, between 60°C and 120°C. Below, temperature becomes too high and petroleum and kerogen are transformed into gas by thermal cracking. Petroleum - a liquid - is originating mainly from soft organisms such as algae and bacteria, whereas coal - a solid - is mainly derived from hard organisms such as trees.
To conclude, the Maillard reaction allows explaining, at least partly, the formation over geological times of three major sources of energy and matter: petroleum, coal and gas. Humans are now burning rapidly petroleum, coal and gas, thus releasing carbon dioxide, a greenhouse gas, into the atmosphere. Fossil resources being limited, scientists are now trying to transform renewable matter such as trees, crop residues and sewage sludges into petroleum by heating.
Dr. Eric LICHTFOUSE
Earth Sciences Department
INRA-University of Burgundy
6, Bd Gabriel
21000 Dijon, France
Eric.Lichtfouse@u-Bourgogne.fr
Tel/fax 33 3 80 39 63 72
http://www.u-bourgogne.fr/ACE/Z00Licht.html
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How is oil formed according to the French Petroleum Institute ?
L results from organic the thermal matter degradation contained in certain rocks: the "roches mères" oil. They are fossilized remainders of watery or terrestrial plants and bacteria accumulating at the lake, ocean floor or delta. Called "kérogène", these organic residues are preserved in environments where water is deprived d oxygene, thus mixing with the mineral sediments to form the bed rock. During tens of million years, new sediments will continue with s'accumuler, involving the bed rock with great depths. Generally between 2500 and 5000 m and under the action of the high temperatures which reign there, the kerogen are transformed (thermal cracking) into liquid oil accompanied by gas. With more than 5000 m, oil "craque" in its turn and transforms itself into gas. Lighter than water, oil and gas go up along the levels of porous rocks (rock tank) in which they are confined if those are surmounted impermeable rocks (rock cover). If nothing stops them, they ooze on the surface. C'est l'origine of the "mares" of oil (exploited during l Antiquity and described by Marco Polo) that l'on can see for example with the Middle-East or Venezuela. If they meet "défauts" in the system of drains which carries out them towards surface (such as folds) they come s'y to accumulate. They are these traps with oil and gas which seek the oil explorers. *
