Predicting the quantities of oil and gas generated fromAustralian Permian coals, Bowen Basin using pyrolyticmethods

The aim of the study was to establish kinetic parameters for gas and oil generation and totest the applicability of the kinetic models to petroleum generation through comparisons withnatural maturity coal sequences (433°C<Tmax<547°C; 0.53%<Ro<2.59%) and field observations in theBowen and Surat basins. From bulk pyrolysis and py–gc, the quantities and composition ofcoal-derived products have established that the oil window is between 440 and 465°C (0.7%<Ro<1.2%). This compares favourably with the oil window defined using the chemical kinetics model(0.1<TR<0.5; 0.65–0.7%<Ro modelled<1.05–1.2%) applied to the geohistory model as well asencompassing the range in chemical maturities of the oils (0.65<Ro calculated<1.05%) in theBowen and Surat basins. Furthermore, field observations on gas maturity (1.05%<Rocalculated<1.4%) support the kinetic predictions that the bulk of the gas generation mainly occursafter bulk oil generation. However, there are specific discrepancies that question the currentkinetic treatment for coal and its ability to accurately predict petroleum generation in thesubsurface. For example, the naturally matured coals are more oil prone, as a result ofre-incorporation of H-rich volatile components into the coal matrix, compared with predictionsfrom the immature analogue. Furthermore, cumulative GORs determined from modellingsignificantly underestimate GOR found for recoverable gas and oil from the Bowen and Suratbasins. Here, uncertainties in the extent of gas and oil preservation arising from multiple phasesof petroleum generation during a complex burial history model may also be significant.