Molecular changes in the organic geochemistry of the Vaca Muerta Shale Formation as consequence of natural maturation

ANDRÉS DONADELLI, JORGE; CANNEVA, ANTONELA; GARRO LINCK, YAMILA; MARTINEZ DELFA, GERARDO; ERRA, GEORGINA; VELASCO, MANUEL I.; FRANZONI, MARÍA B.; SILLETTA, EMILIA V.; HECTOR ACOSTA, RODOLFO; CALVO, ALEJANDRA

ORGANIC GEOCHEMISTRY

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2021

0146-6380

The Vaca Muerta Formation, located in the NeuquénBasin (Argentina), is one of the most important shale plays in the world. A detailed organic matter structure characterization of the formation and its evolution during maturation is a must for the correct evaluation of petroleum potential. The present work studies molecular characteristics of organic matter of samples from several wells within the formation. Speciation of organic carbon, oxygen, nitrogen, and sulfur present in rocks are analyzed by XPS and 13C solid-state NMR and compared to typical geochemical analyses: pyrolysis and solid bitumen reflectance. Samples present a high TOC and cover a wide range of maturity levels (%BRo between 0.7-1.6%). Differences in carbon aromaticity measured by 13C NMR and XPS are discussed. Carbon, nitrogen, and sulfur present in organic isolates are studied and compared to reported data of several shale formations (Duvernay, Bakken, Woodford and from the Bohai Bay Basin). Results are a novel contribution for understanding and modeling organic matter in the Vaca Muerta Formation and can be used to support and improve the classification of kerogens based on their molecular structure.