Year

1987

Degree Name

Doctor of Philosophy

Department

Department of Chemistry

Abstract

Oil shale samples from the upper and lower units of the bipartite Duaringa oil shale deposit, Queensland Australia, have been analysed using a variety of fast characterisation procedures such as solvent extraction, pyrolysis-GC, isothermal pyrolysis and TGA. A CDS-150 pyroprobe was modified to simulate Fischer assay retort conditions on a micro scale basis and was used for the rapid assessment (pyrolysis-FID) of the hydrocarbon generating potential of these and other oil shale samples. Results obtained for Duaringa were extended to analytical studies on an extensive range of selected Australian and several overseas reference oil shales. An electronically-controlled tube-furnace retort was constructed to provide accurate control over heating rates and pyrolysis environments. The retort was used to produce shale oils for samples from both units of the Duaringa deposit, which were then compared with each other and with a Duaringa reference oil obtained using the conventional Fischer assay procedure. The retort was also used to study the composition of pyrolysate produced over narrow sequential temperature ranges to provide better understanding of retort processes and pyrolysis mechanisms.

Solvent extracts of the Duaringa lamosites contain a homologous series of linear alkanals not previously reported in Australian oil shales. Following their characterisation the Duaringa bitumen (based on mass-spectral data and retention-index values) these aldehydes were subsequently detected in extracts from other Australian oil shale deposits. The possible origins and significance of these and other components found in oil shale bitumen are discussed in relation to the source, environment of deposition, maturation and bio-degradation of the kerogen comprising these deposits.

Results obtained from the pyrolysis-FID procedures for Duaringa were used to characterise (type) the Australian and overseas oil shales on the basis of their relative abilities to generate (type-dependent) quantities of hydrocarbons (oil and gas) from the pyrolysis of their raw shale. For shales comprising type I and II organic matter, hydrocarbon oil and gas yields correlated positively with Fischer assay oil yields,petrographic data, kerogen content and elemental composition. The procedure provides a rapid and inexpensive screening method for the accurate first assessment of the relative -generating potential of a given deposit.

Retort oils from the upper unit (resource seams) and lower unit (> 1000 m) were analysed by extraction and column chromatography, followed by detailed gas chromatography and mass spectrometry of each of the 19 fractions isolated. Hundreds of compounds were identified and their retention indices calculated where the components eluted as discrete peaks in respective gas chromatograms. Least-squares linear regression analysis of these data allowed retention-index equations to be calculated for a wide variety of different compound classes. Collectively this information provides reference data which should allow comprehensive chemical characterisation of shale oil to be achieved without the need for mass spectrometric analysis of each column fraction.

Despite the substantial difference in the depth of burial, the chemical composition of the upper- and lower-seam Duaringa shale oils was very similar and found to resemble those from non-carbonaceous seams of other Tertiary Australian deposits (Condor and Rundle). The distribution and relative abundances of some of the isomeric structures encountered in each of them indicate that retort-product concentrations are influenced by relative variations in the thermocatalytic activity of the mineral matrix. Accurate and class-specific quantitative data obtained for Duaringa phenols, nitriles and ketones suggest that these volatile components constitute only a minor portion of the otherwise non-volatile column fractions in which they are found. This implies that gravimetric data published for these compound classes for Condor and Rundle shale oils overestimate their abundance.

Data obtained from rapid characterisation techniques were interpreted in relation to the composition of the corresponding retort oils. Advantages and limitations of microscale screening techniques are discussed with reference to results obtained for Duaringa and other Australian oil shale deposits.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.