Characterisation of fluid inclusion oil in a Mid-Proterozoic sandstone and dolerite (Roper Superbasin, Australia)

The Bessie Creek Sandstone fluid inclusion oil was generated in the peak to late oil window (∼0.9-1.0% VRE). The higher molecular weight (C13+) proportion of the dolerite feldspar fluid inclusion oil is of lower maturity (∼0.8% VRE) than the same molecular weigh range fluid in the Bessie Creek Sandstone fluid inclusion oil. Both of these oils were most likely generated in the overlying Velkerri Formation, however, the volumetrically dominant low molecular weight hydrocarbons in the dolerite feldspar fluid inclusion oils have a higher maturity (∼1.3% VRE), and may have been generated from the deeper, ca. 1600 Ma Barney Creek Formation in the underlying McArthur Group. This study shows that oil trapped in fluid inclusions has a greater potential to preserve pristine organic geochemical information than porosity-bound oils and dispersed kerogen. If oil inclusions occur in sufficient abundance the analysis of these tiny oil encapsulations is technically feasible, and can give valuable information on the composition of the Earth's early biosphere and Precambrian petroleum systems.