Geochemical assessment of oils from the Mero Field, Santos Basin, Brazil

• Published in: Organic geochemistry Vol. 130; pp. 1 - 13
• Main Authors: Rocha, Ygor dos Santos, Pereira, Rosana Cardoso Lopes, Mendonça Filho, João Graciano
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-04-2019
• Subjects: Biomarkers; Crude oil; FT-ICR MS; Lacustrine oils; Petroleomics; Polar compounds; Pre-salt; Santos basins; FT-ICR MS; Lacustrine oils; Crude oil; Biomarkers; Santos basins; Polar compounds; Petroleomics; Pre-salt
• ISSN: 0146-6380; 1873-5290
• DOI: 10.1016/j.orggeochem.2019.01.011

•Petroleomics of crude oils recovered from the Mero Field, Santos Basin, Brazil.•The samples were generated under a thermal condition related to the peak of the oil window (0.7–0.9%Ro).•The samples were generated by a source-rock deposited in a lacustrine environment.•ESI FT-ICR MS is a trustworthy way to achieve a geochemical assessment.
Three crude oils recovered from three different wells of the Mero Field in the pre-salt of the Santos Basin were selected for detailed geochemical analysis. The samples were analyzed using a 7.2 T LTQ FT-ICR MS instrument by negative electrospray ionization (–ESI), focusing on the polar compounds, i.e., nitrogen-, sulfur-, and oxygen-containing compounds (NSO). Additionally, a combination of traditional geochemical methods including GC-FID, GC-MS, and carbon isotopic composition (whole oil and n-alkanes) were used to assess the samples. Through this work, it was demonstrated that –ESI FT-ICR MS is a reliable method for assessing crude oil composition and providing information about the origin and thermal maturity of the samples. Results showed that the dominant heteroatom classes are N1, O2, N1O1, and O1. Due to the similarity of double bound equivalent (DBE), which means number of unsaturation present in an organic molecule, and carbon number distributions for the N1 class species it is possible to suggest that Mero's filling history had an oil charge representing the peak of the oil window (0.7–0.9 %Ro) and that the oils were generated by a source rock deposited in a lacustrine environment.