HYDROCARBON DISTRIBUTION IN THE IRATI SHALE OIL

This work reports a detailed characterization of the various hydrocarbon structures present in a sample of the Irati shale oil (Sao Mateus do Sul, Parana), obtained by the Petrosix Process, by means of a combination of gas chromatography-mass spectrometry (g.c.-m.s.), co-injection with authentic standards, and retention time data of model compounds. Hydrocarbon structures, the main constituents of the shale oil (approximately 38 wt%), include: linear, branched and isoprenoidal alkanes, linear and isoprenoidal alkenes, alkylcyclopentanes and cyclohexanes, alkylcycloalkenes, hopenes, hopenes and steranes. Linear structures are dominant (43% of the total hydrocarbons), followed by isoprenoidal skeletons. Saturated compounds strongly predominate over their unsaturated counterparts. The use of several maturity parameters attested to the immaturity of the sediment. Our data further suggested a predominant algal/microbial origin and a basic lacustrine depositional environment to the Irati shale, probably under a moderate oxidative condition, thus confirming previous conclusions obtained via analysis of the Irati bitumen and the shale rock. Additionally, the data confirmed the usual classification of this shale as containing Type-II kerogen.