Abstract

Several studies have indicated the presence of more than one generation of bitumen that could be isolated from rocks through sequential extraction or after demineralization or both. Nabbefeld et al. (2010a) and Holman et al. (2012, 2014) termed bitumen obtained after solvent extraction from the undigested rock as “Bitumen I" and that obtained by extraction after demineralization of rock as “Bitumen II.” The occurrence of different bitumen fractions in rocks poses the question of whether subsequent bitumens are of the same origin as those of the first generation, remaining trapped in the rock matrix and unable to be easily extracted, or if they originated from different source. Based on the distinct composition of Bitumen I and Bitumen II in Paleoproterozoic marine rocks in Australia, Williford et al. (2011) and Holman et al. (2012, 2014) suggested that Bitumen II was closely related to the in-situ organic matter, whereas Bitumen I could be over- printed by migrated hydrocarbon phases. The investigation includes the chemical functional group characteristics and origin of different bitumen fractions present in Jurassic to early Cretaceous Vaca Muerta Formation from Argentina. The main objectives of the paper were to relate the differences in chemical functional groups of the two bitumen fractions to their origin in correspondence to kerogen macerals present in Jurassic to early Cretaceous Vaca Muerta Formation from Argentina. The impact of thermal decomposition of kerogen to Bitumen I and Bitumen II was discussed with regard to hydrocarbons mobilization in shales. The research is broadly described in Malachowska et al., 2019.

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