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Geochemical Fingerprinting Applications in Petroleum System Assessment


Geochemical fingerprinting is one of the essential methods to determine the origin and the reservoir connectivity of oils that possess variable chemical compositions and physical properties. This study aims to demonstrate various oil-oil and oil-source geochemical correlation techniques that consider the variation in physical properties, to assess the reservoir compartmentalization and communication and oil source rocks. A total of eight representative oil samples were selected from different oil accumulations from a single petroleum system. The study uses various gas chromatography (GC) techniques, including C7 light hydrocarbon GC oil correlation star diagram, C8-C20 whole-oil GC multivariate statistical fingerprinting, and biomarkers. Moreover, the oil samples were characterized for their API gravity using a density meter. The first group of oils were located in deeper settings compared to the others, and characterized by relatively high API gravity values that range from 37.5° to 39°. The other groups have medium to heavy API gravity values. The C7 light hydrocarbon GC oil correlation star diagram reveals that the oils share the same fingerprint, suggesting a similar source rock. This was further confirmed by the biomarker results, which suggested same source rock characteristics. The C8-C20 whole-oil GC fingerprinting discloses that the studied oils are not in communication and might represent three separate compartments. The observed variations in bulk properties of these oils can be attributed to in reservoir alteration or/and migration processes, such as water washing and biodegradation. This study concludes that by using various geochemical fingerprinting techniques, the oil to source correlation can be accomplished, regardless of the variability in the physical and chemical properties.