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

Carlos Boente,Patricia Marín,Marco Antonio Guzmán,Emilio Romero,Gonzalo Márquez,Cristina Rodrigues

doi:10.3390/ijerph17197204

Abstract

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 n-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.

Highlights

Angola is one of the largest crude oil producers in Sub-Saharan Africa
The N–S-striking 200-km-long Lower Congo Basin (LCB) extends from the coastline in the east to the escarpment at the base of the Angolan slope in the west [9]
LCB is one of the numerous salt sub-basins that developed during the opening of the West African passive margin in the early Cretaceous [10]

Summary

Introduction

Angola is one of the largest crude oil producers in Sub-Saharan Africa. The country produces about 1.8 million barrels per day after a boom from 2002 to 2008 as its deepwater fields began to take off. Crude oil production comes almost entirely from offshore fields off the coast of Cabinda and deepwater fields in the Lower Congo Basin (LCB). Angola began producing oil in 1956, when the company Petrofina discovered the first accumulation near Benfica in the Kwanza Basin, and has estimated crude oil reserves of 13 billion barrels. Most of the proved reserves are located in the offshore parts of the Lower Congo and Kwanza basins, which developed during the Late Jurassic and Neocomian times on the conjugated margins of Africa and Brazil. Public Health 2020, 17, 7204; doi:10.3390/ijerph17197204 www.mdpi.com/journal/ijerph

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