Wednesday, 22 August 2007
Mini Fractionation of Crude Oil
Analysis of crude oils is often undertaken to evaluate source rocks and their depositional environments. Carbon isotope analysis of the saturate and aromatic fractions of the oil as part of the testing process, is used to identify if the oil is of terrestrial or marine origin.
The carbon isotope analysis requires less than a milligram of each fraction for analysis so in our lab we use a 'mini fractionation' procedure to prepare the two fractions. This involves using a glass pasteur pipette as column to hold a bed of activated silica gel. A few microlitres of the crude oil sample is placed on top of the bed and the saturate fraction eluted with with hexane (picture on left). Once all the saturates have been washed through, the aromatics are eluted with toluene (picture on right). Each fraction is then blown dry under nitrogen and are then analysed on one of the EA-IRMS systems.
This simple and robust procedure for obtaining carbon-13 data that can be used to identify the source of the crude oil was developed in collaboration with one of our clients, Dr Matthew Kaye of OceanGrove Geoscience Ltd.