UnravelingGeochemical Assessment from FT-ICR Data:Comprehensive Analysis of the Crude Oil Depositional Environment

Abstract In petroleum exploration, understanding geochemistry is crucial for distinguishing between different types of crude oil based on their depositional environments. Traditional biomarkers found in saturated and aromatic fractions have long been used for this purpose; however, they often fail to provide a comprehensive picture because they provide limited information on heteroatom-containing compounds. Despite being present in smaller quantities, polar compounds hold valuable geochemical information that can complement or even replace conventional biomarkers. The advent of Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) has revolutionized crude oil geochemistry by enabling the precise characterization of these polar and apolar components. In this study, we focus on the characterization of 79 crude oil samples from diverse Brazilian sedimentary basins shaped by the separation of South America and Africa using the APPI(+) FT-ICR MS. We suggest that the ternary diagram of N, O, and S heteroatomic classes separates oil saline lacustrine from freshwater lacustrine and marine/transitional. The ratios of (DBE 1–4/ΣDBE 16–27 of the S class and DBE 4–6/ΣDBE 10–19 of the HC class) are useful to separate marine from transitional oil samples. The DBE 5/DBE 10 and DBE 5/DBE 3 ratios, calculated using the sum of C15–40 carbon numbers of the DBE 3 in the S1 class, distinguish all types of origins in this study. A high abundance of C40 HC and S1 was applied to differentiate the saline/redox conditions of the samples. We aim to refine oil classification and depositional-environment reconstructions, thereby enhancing the accuracy and depth of crude-oil geochemical analysis.