Multivariate statistical analysis of diamondoid and biomarker data from Brazilian basin oil samples

Diamondoids are compounds commonly found in oils. Highly stable, they are more resistant to thermal and biological destruction than other hydrocarbons. Diamondoid-derived parameters have been used to assess the degree of thermal evolution and the extent of secondary cracking of light oils and condensates and in the identification of mixtures of oils from distinct migration pulses. Twenty-one samples of oils from five sedimentary basins of Brazilian continental margin were selected and studied on diamondoids and biomarkers. The oil samples were analyzed by gas chromatography coupled to mass spectrometry and principal components analysis (PCA) aiming to correlate biomarker and diamondoid parameters. Diamondoid and biomarker ratios analyzed by PCA led to a more accurate assessment of the maturity of the oils. The combination of diamondoid data with biomarker parameters also allowed to rank the oils from one of the five basins (JX basin) as the most mature oils, while oils from another basin (JE basin) were classified as mixtures formed from different pulses of migration.