Classical Biomarker and Quantitative Extended Diamondoid Analysis Fingerprints for Crude Oils from Deepwater Developments in Block 17, Lower Congo Basin, Angola

• Main Authors: Carlos Boente, Gonzalo Márquez, Patricia Marín, Emilio Romero, Cristina Rodrigues, Marco Antonio Guzmán
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: International Journal of Environmental Research and Public Health
• Subjects: Block 17; mixed oils; QEDA analysis; PM biodegradation scale; Lower Congo Basin
• Online Access: https://www.mdpi.com/1660-4601/17/19/7204

The organic geochemistry of six oil samples from the offshore Block 17 (Lower Congo Basin, northwestern Angola) was studied by a combination of classical biomarker and extended diamondoid analyses to elucidate source rock facies, the extent of biodegradation, and thermal maturity. Based on molecular data, oils are interpreted as depicting a mixture of two pulses of hydrocarbon generation probably from the Bucomazi and Malembo formations. Geochemical results also gave evidence of mixing of a lacustrine siliciclastic-sourced oil charge and a second more terrestrially derived oil type in the samples analyzed. A single genetic oil family was identified through hierarchical cluster analysis; however, two groups of oils were identified on the basis of their biodegradation levels using the Peters/Moldowan scale. Lower and upper Malembo oils have a slight depletion and a notable absence of <i>n</i>-alkanes, suggesting PM levels of 1 and 2, respectively. Most molecular maturity parameters of the oil samples suggest a maturity level equivalent to the onset of the peak of the oil generative window.