Fractionation of pyrrolic nitrogen compounds in petroleum during migration: derivation of migration-related geochemical parameters

Abstract

Abstract Analysis of a range of crude oils and source rocks appears to indicate that primary and secondary oil migration has a strong impact on the distribution of pyrrolic nitrogen compounds in reservoired petroleum. The migration effects controlling the composition of pyrrolic nitrogen compounds recognized tentatively in this study include (a) the relative enrichments of alkyl carbazoles to alkylbenzocarbazoles, (b) nitrogen-shielded isomers to nitrogen-exposed isomers, and (c) higher homologues to the lower homologous species. A suite of molecular migration parameters based on chemical compositions of pyrrolic nitrogen compounds in crude oils have been proposed. If substantiated in more case history studies, these parameters are potentially useful in petroleum population mapping.