Crude oils from Austral and Golfo San Jorge Basins. Similarity and differences based on Biomarker Ratios

Abstract

The biomarker profiles are characteristic of oils. The goal of this study was to evaluate the biomarkers in oil samples using geochemical analysis. Oil samples were obtained from Austral Basin and from Golfo San Jorge Basin. Specifically, the aliphatic and aromatic fractions were analyzed by Gas Chromatography coupled to Mass Spectrometry. Biomarker ratios were calculated for isoprenoids, terpanes, steranes to correlate the organic matter precursor, deposition environment, and others to differentiate distinct crude oil sources. Based on the specific parameters, the crude of the Austral Basin appears to have been generated from organic matter type II-III (mixed), in deposition environments with moderate oxygen concentration, associated with a siliciclastic lithology and a moderate to high thermal maturity. On the contrary, the crude oils from the Golfo San Jorge Basin displayed biomarkers profiles characteristics to a type II (marine) kerogen, corresponding to an anoxic deposition environment, carbonated lithology and low thermal maturity.