Comparaciones basadas en biomarcadores de crudos extraídos de la formación Springhill (Cuenca Austral) y de la formación bajo Barreal (Cuenca Golfo San Jorge), Argentina
Date
2022-01
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
En Argentina existen varias cuencas productivas de petróleo, entre ellas las Cuencas Golfo San Jorge y Austral. Sus sucesiones estratigráficas contienen varias unidades que actúan como rocas reservorio, destacando en este estudio las formaciones Bajo Barreal (98 Ma) y Springhill (134 Ma). El objetivo de este trabajo fue comparar crudos extraídos de estas formaciones usando biomarcadores geoquímicos orgánicos: saturados (n-parafinas, isoprenoides acíclicos pristano y fitano, esteranos y terpanos) y aromáticos (fenantrenos y dibenzotiofenos) para establecer similitudes y diferencias respecto al tipo de materia orgánica que les dio origen, el grado de biodegradación alcanzado por los mismos y, por otro lado, determinar la litología y las condiciones de depósito que controlaron la acumulación y preservación de la materia orgánica en sus rocas madre. Los crudos fueron sometidos a una separación de sus fracciones alifáticas y aromáticas por cromatografía de adsorción sólido-líquido en columna y cada uno de estos extractos obtenidos fue analizado mediante cromatografía de gases acoplada a espectrometría de masas (GC-MS). A partir de las relaciones de diagnóstico, calculadas con las abundancias relativas de los biomarcadores, se sugiere para los crudos de la Formación Springhill que la materia orgánica precursora fue de tipo mixto marino - continental, depositada en un ambiente con concentración moderada de oxígeno (disóxico-subóxico), en el cual la roca madre se caracterizó por ser de naturaleza marina siliciclástica, y no se observó biodegradación de estos. Por otro lado, los crudos asociados a la Formación Bajo Barreal son de tipo algal-lacustre severamente biodegradados, sedimentados en condiciones de anoxia en una roca generadora tipo carbonática. Estos resultados concuerdan con estudios previos realizados sobre crudos provenientes de otros yacimientos de ambas formaciones, pero lo novedoso radica en que estas localizaciones nunca fueron estudiadas.
In Argentina, there are several crude oils-producing basins, including the Golfo San Jorge and Austral basins. Their stratigraphic columns present several units that behave as reservoir rocks, the Bajo Barreal and Springhill formations stand out in this study. The objective of this work was to compare crude oils extracted from these formations using the organic geochemical biomarkers: saturated (n-paraffins, acyclic isoprenoids pristane and phytane, steranes and terpanes) and aromatic (phenanthrenes and dibenzothiophenes), with the purpose of evaluating similarities and differences in order to establish the crude oil precursor organic matter type, the biodegradation degree and, the lithology and depositional conditions that controlled the accumulation and preservation of organic matter in theirs source rock. These crude oils were subjected to separation of their aliphatic and aromatic fractions by solid-liquid adsorption and column analyzed each one by gas chromatography-mass spectrometry (GC-MS). From the diagnostic ratios, calculated from the relative abundances of the biomarkers, it is suggested for the Springhill Formation crude oils that the organic matter source (mixed marine-continental), were deposited in a sedimentary environment with moderate–to-low oxygen concentration (disoxyc-suboxyc), in which the source rock was characterized as shelf marine shales and no biodegradation was observed. On the other hand, the crude oils associated with the Bajo Barreal Formation can be classified as a severely biodegraded algal-lacustrine type, deposited in anoxic conditions in a carbonate source rock. These results are in agreement with previous studies carried out on crudes from other reservoirs in both formations, but the novelty is that these locations have never been studied.
In Argentina, there are several crude oils-producing basins, including the Golfo San Jorge and Austral basins. Their stratigraphic columns present several units that behave as reservoir rocks, the Bajo Barreal and Springhill formations stand out in this study. The objective of this work was to compare crude oils extracted from these formations using the organic geochemical biomarkers: saturated (n-paraffins, acyclic isoprenoids pristane and phytane, steranes and terpanes) and aromatic (phenanthrenes and dibenzothiophenes), with the purpose of evaluating similarities and differences in order to establish the crude oil precursor organic matter type, the biodegradation degree and, the lithology and depositional conditions that controlled the accumulation and preservation of organic matter in theirs source rock. These crude oils were subjected to separation of their aliphatic and aromatic fractions by solid-liquid adsorption and column analyzed each one by gas chromatography-mass spectrometry (GC-MS). From the diagnostic ratios, calculated from the relative abundances of the biomarkers, it is suggested for the Springhill Formation crude oils that the organic matter source (mixed marine-continental), were deposited in a sedimentary environment with moderate–to-low oxygen concentration (disoxyc-suboxyc), in which the source rock was characterized as shelf marine shales and no biodegradation was observed. On the other hand, the crude oils associated with the Bajo Barreal Formation can be classified as a severely biodegraded algal-lacustrine type, deposited in anoxic conditions in a carbonate source rock. These results are in agreement with previous studies carried out on crudes from other reservoirs in both formations, but the novelty is that these locations have never been studied.
Description
Keywords
Formación Springhill, Formación Bajo Barreal, Cuenca Austral, Cuenca Golfo San Jorge, biomarcadores, crudo, Springhill formation, Bajo Barreal Formation, Austral Basin, Golfo San Jorge basin, biomarkers, crude oil
Citation
Collections
Endorsement
Review
Supplemented By
Referenced By
Creative Commons license
Except where otherwised noted, this item's license is described as openAccess