Heterocyclic aromatic hydrocarbon distributions in petroleum: A source facies assessment tool

Abstract

This study reports a novel source facies assessment application from distributions of heterocyclic aromatic hydrocarbons in petroleum, i.e., dibenzothiophene (DBT), dibenzofuran (DBF) and fluorene (F). To illustrate the approach initially, a large set of crude oils from global petroleum basins are geochemically characterized based on source facies, organic-matter type and environment of deposition variation. Petroleum bulk properties and molecular distributions of isoprenoids, terpanes, steranes and related parameters are applied to demonstrate the source facies and maturity of the entire oil suite and to delineate the oil suite into marine carbonate, marine shale, marine shale with terrigenous organic matter (OM), coaly and lacustrine source-facies families. From within this interpretive context, the relative percentages of hetercyclic aromatic hydrocarbons are reported and discussed from each of these source-facies families. A triplot drawn from the percentages of DBT, DBF and F is shown to effectively differentiate the oils source-facies classifications. Marine carbonate oils show highest %DBT plotted in the DBT vertex, freshwater lacustrine-sourced oils positioned near to 100% F vertex, coaly-sourced oils revealed highest %DBF. The marine shale and marine shale with terrigenous-OM oil families plotted away from three vertices and represent a distinctive position with in the triplot. These results establish an effective source-facies assessment tool triplot based on heterocyclic aromatic hydrocarbon distributions. These novel signatures which are derived from variations in the chemical composition of source rocks, hence kerogen, lead to the occurrence of kerogen catalysis in sedimentary reaction (like carbon catalysis) for the formation of heterocyclic aromatic hydrocarbons.