APPLICATION OF COMPUTERIZED GAS CHROMATOGRAPHY – MASS SPECTROMETRY TO OIL EXPLORATION IN AUSTRALIA

Abstract

Computerized gas chromatography-mass spectrometry (C-GC-MS) is a sophisticated analytical technique capable of identifying very small quantities of individual components in complex mixtures of organic compounds. One field in which C-GC-MS can play an extremely important role is correlation studies of crude oils and source rocks.

In C-GC-MS analyses, compounds present in the crude oil or source rock extract are first separated by the gas chromatograph and then fragmented and ionized in the ion source of the mass spectrometer. The mass and relative intensities of the ions formed are recorded by the computer. Normally the masses of one or two specific fragments can be used to distinguish as particular class of compounds, a technique that is particularly useful for crude oil correlation studies.

Comparison of mass fragmentograms for different oils yields information about their sources. Identical fragmentograms for ion characteristics of certain classes of "biological marker" compounds imply that the distribution of compounds in the oils is identical and hence that the oils had the same or very similar sources.

Results of C-GC-MS analysis of four oils from the Gippsland Basin indicate that, despite varying degrees of biodegradation, the oils had the same or very similar source materials. Similarly C-GC-MS analysis of the Barrow Jurassic and Windalia oils from the Carnarvon Basin provides evidence to support the theory that these two oils had the same or very similar source material.