Biodegradation of oils in the Norne-Svale-Falk Trend – The Halten Terrace – the effects of enzymatic selectivity of bacteria on oil quality

It is not generally realized that bacteria utilize oils as a source of energy, nor that petroleum compounds migrate to the sea-bed of all marine sedimentary basins, providing a source of energy for the biota.

The scope of this thesis is to evaluate the effects of biodegradation in a series of oils in the northern part of the Halten Terrace. Biodegradation of oils is a naturally occurring process that occurs under oxic conditions and at temperatures no higher than about 70-80°C. Bacteria extract the negative entropy in the hydrocarbon (HC) fraction of oils and are also able to assimilate certain aromatic HC compounds with the right steric configuration.

Migration of petroleum up from the basin to the west (Fig. 1) of oil-traps in the Norne-Svale trend is likely to be ongoing today, and oil in deep and hot traps, like Norne and the even deeper Alve, is “virgin” and non-biodegraded, while the oil in shallower traps, like Svale, Linerle and Falk, are progressively and systematically degraded.

The order of attack on oils by bacteria follows stringent systematics with n-alkanes being attacked first, and tricyclic triterpanes as some of the last, together with aromatic HCs where the attack can be very isomer-specific. The result is always that oils become heavier in terms of gravity, and richer in asphaltenes and resin, and lover in alkanes – a fact that has an effect on the commercial price of the oil, and oils in e.g. Venezuela are notoriously heavy due to this effect.

The student will in this project learn about analytical methods such as liquid chromatography, GC-FID and GC-MS methodologies, biomarkers (BM) and geomarkers (GM) and oil trap filling as a dynamic process. The aim is to understand better the systematics of this “Petroleum System”.

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Fig. 1. A series of oil and condensate accumulations in the “trend” from Alve, Norne, Urd/Lerke, Svale to Falk with the northern Linerle accumulations. (Factmaps NPD, see for details. | Click here for a bigger picture. 


Published Sep. 20, 2021 10:12 AM - Last modified Sep. 20, 2021 10:12 AM


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