Source Rock Distributions and Petroleum Fluid Bulk Compositional Predictions on the Vulcan Sub-basin, Offshore Western Australia

Several scenarios of an original 3D model based on the petroleum systems model of Fuji et al. (APPEA 2004) were simulated using the PetroMod 3D V.10 modeling software. In general the results of the modelling study presented here confirms the modelling results of Fuji et al. (2004) with respect to the timing of generation in the different sub-basins as well as present day maturity. The main differences between the work of Fuji et al. (2004) and the work presented here are based on the use of PhaseKinetic models for the individual source rock formations and the ensuing compositional predictions of the fluids in different fields. Source rock transformation ratios as well as the bulk generation rates indicate that the source rocks are presently still generating. The Central Swan Graben area is presently more mature than the other kitchen area of the Vulcan Sub-basin, the Cartier Trough. The locations of predicted accumulations coincide with the locations of most of the proven fields. In many cases accumulation sizes and predicted column heights are large, mainly due to the fact that the resolution of the numerical model is low which leaves rather large volumes of the cells to be filled. Modelling results predict a series of accumulations at locations which have, as yet, not been tested. However, most of them depend on fault closure, thus increasing exploration risk. The main risks as observed from this modelling exercise are: 1) source rock presence and definition, 2) definition of the traps, 3) resolution of the input model, 4) cap rock properties, which are still largely unconstrained. The different scenarios modelled show distinct variations with respect to predicted petroleum distribution as well as the physical properties of the accumulated fluids.

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