Development of method for evaluating oil mixtures in different Brazilian oil reservoirs
Name: BRUNO FIORESI PAQUELI
Publication date: 04/03/2026
Examining board:
Name |
Role |
|---|---|
| BRUNO QUIRINO ARAUJO | Coorientador |
| EUSTAQUIO VINICIUS RIBEIRO DE CASTRO | Presidente |
| GABRIELY SILVEIRA FOLLI | Examinador Interno |
| PAULO ROBERTO FILGUEIRAS | Examinador Interno |
| VINÍCIUS BARRETO PEREIRA | Examinador Externo |
Summary: Biodegradation and oil mixing processes have been extensively investigated in the literature and have already been documented in Brazilian petroleum systems. The traditional assessment of these processes involves the qualitative analysis of the chemical profile and biomarkers using GC–MS. In this context, the aim of this work was to apply different methods to assess biodegradation and oil mixing in a set of crude oils from Brazilian sedimentary basins. First, the biomarker assessment with emphasis on the diamondoid class, performed on a set of five crude oils, allowed the identification of one non biodegraded oil, two biodegraded oils, and two oils showing oil mixing behavior. The second objective was to develop a method to evaluate these processes using FT–MIR using 31 oil samples and binary mixtures prepared from two endmembers. The results showed that indices based on ratios between spectral bands were effective in separating non-biodegraded, intermediate, and biodegraded oils, especially the CH sp3/1500–650 cm–1 ratio. PCA and HCA analyses further indicated that the intermediate oils exhibited a profile similar to that of the prepared mixtures, suggesting that they correspond to mixtures of non biodegraded and biodegraded oils. The third objective was to investigate the chemical profile of these same 31 oils using GC–MS and GC–FID. The results demonstrated that the calculation of 25NH/H30, peak/hump, SAT/ARO, and SAT/POL ratios, together with exploratory analyses such as PCA and HCA, showed the ability to separate the oils into biodegraded, intermediate, and non biodegraded groups, also identifying oils that showed distinction (outliers) within the same group, suggesting mixing processes with a greater impact on the oil profile. Finally, it was verified that the association of different tools and analytical methods enabled the characterization of the oil set in relation to the secondary alterations undergone over the years of accumulation in the reservoir.
