| Summary: | Establishing genetic correlations between oils and between oils and their source rocks is especially difficult in basins with multiple source rocks where oil mixing has occurred. It is therefore of paramount importance to employ multiparameter approaches based on a combination of source-related molecular markers across different fractions of oils and source rock extracts in order to perform meaningful oil-oil and oil-source correlations rather than simply relying on classical correlation protocols based on biomarkers. Furthermore, the complexity of petroleum mixtures demands that compound-specific isotope analysis (CSIA) rather than bulk isotope analysis are implemented, as CSIA enables the identification of multiple organic matter sources in oils, condensates and source rock extracts by comparing the isotopic compositions of individual hydrocarbons of different chain length. The main objective of this dissertation has been to investigate the source, maturation, alteration and mixing of petroleum in two basin-specific case studies, (1) the Hammerfest Basin (HB), Norwegian Barents Sea and (2) the South Viking Graben (SVG), Norwegian North Sea. For this purpose, multiparameter approaches that combine the molecular composition of different petroleum components, such as light hydrocarbons, n-alkanes, sterane and triterpane biomarkers, resin-derived biomarkers, heterocyclic and polycyclic aromatic hydrocarbons in conjunction with compound-specific stable carbon and hydrogen isotope compositions of alkanes have been employed. The present research work also addresses the issue of how best to unravel and quantify the relative input of different source rocks contributing to mixed oils using δ13C values of individual petroleum hydrocarbons. Molecular and isotopic evidence revealed distinct petroleum mixing processes involving source, age and thermal maturity variations in reservoirs of the HB. The mixtures originated from hydrocarbons derived from Type-II and Type-III kerogen-rich source rocks, which displayed only small ...
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