Origin of oils in the Velebit oil-gas field, SE Pannonian Basin, Serbia - Source rocks characterization based on biological marker distributions

The Velebit crude oils were generated from siliciclastic source rocks containing a mixture of terrestrial and marine organic matter that was deposited under a predominantly reducing environment, probably in the distal marine portion of a delta. Maturation parameters indicated significant thermal maturity corresponding to peak oil generation. Age-diagnostic biomarker ratios suggest that the source of Velebit oils may be Upper Cretaceous, older than most oils in the Pannonian Basin, which are generated from Tertiary sources. These source rocks are thought to be at a present-day depth of approximately 3000 m, within or in close proximity to, the oil field.