Biodegradation Effects On The Molecular And Isotopic Compositions Of Petroleum Columns: A Case Study From The Alberta Tar Sands

Abstract:

Biodegradation is one of the most dominant post accumulation processes in petroleum reservoirs,
responsible for the huge accumulation of heavy and extra-heavy oils in the world. It causes systematic compositional and physical changes of crude oils by biological alteration in situ, like preferential removal of the low molecular weight compounds and concentration of the heaviest ones, as well as production of acidic compounds, decreases in API gravity and increases in oil density, viscosity, metal and sulphur contents (Head et al., 2003; Peters et al., 2005). Biodegradation levels often change along the oil legs, with most degraded oil generally located close to the oil-water contact, generating compositional and fluid property gradients (Larter et al., 2003).

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