II II II II II - Geoscience Australia

Murray Infra-basins and Oaklands Basin
No hydrocarbon assessments appear to have been published on the largely glaciomarine
Early Permian Urana Formation. Like its correlates in other basins, it may have
appropriate localised source rocks and reservoirs, but finding these would be difficult
and would entail high risk. The best reservoir candidates are the conglomerate and
coarser sandstone fades, formed in beaches, deltas, subaqueous outwash fans, or
current-swept shallow sea beds. The abundant shales and diamictites could furnish
any intraformational seals required. The Late Permian fluvial coal measures of the
Oaklands Basin should contain source, reservoir, and seal lithologies, but with a
vitrinite reflectance of only 0.36% (Middleton, 1989), the rocks are organically
immature.
Tasmania Basin
The only oil production in Tasmania has been on a small scale by distillation from the
Tasmanites oil shales in the northern region of the state (Clarke & others, 1976b).
These developed in nearshore areas following the withdrawal of the ice late in the
Permian 1 interval. Freshwater torbanite is associated with the Mersey Coal Measures
and equivalents, but the occurrences are too limited to be of economic interest (Banks
& others, 1989). The oil shales would be excellent source rocks, were it not for their
general organic immaturity; similarly, the coals and carbonaceous shales in the two
coal measures are only immature to marginally mature, with a peak vitrinite reflectance
of 0.6% away from dolerite intrusions (Banks & others, 1989). It is possible, however,
that in the deep axial portion of the basin organic maturity may have been attained,
and it is pertinent that a show of mature oil in the basal Permian, similar to Tasmanites
oil, has been recorded (BendaII & others, 1991). Reservoir lithologies would be
expected in the fluvial channel fills of the coal measures, in high-energy littoral gravel
or sand bodies such as the Risdon Sandstone (barrier bar, Permian 5) and the
Blackwood Conglomerate (beach gravel, Permian 6), and even perhaps in the basal
glacigene facies in places where sands and gravels have had the opportunity to
become well-washed. However, the presence of hydrocarbons in the glacigene
reservoirs is dependant on the supply from pre-Permian sources, some of which are
noted by BendaII & others (1991) to be within the oil window.
COAL
The Permian is Australia's main source of black coal, which not only supplies the bulk
of the national energy needs, but is currently (1989/90) Australia's largest export
earner. It occurs in all states except Victoria, while in the Northern Territory it is known
only in minor amounts from the Tasman 1 well in the offshore Arafura Basin. The
greatest production by far comes from the Sydney and Bowen Basins: the Sydney
Basin is the largest overall producer (domestic use plus export), whereas the Bowen
Basin has the largest export market. The combined size of the five main eastern coal
basins is comparable to that of the European Carbonifeous coal basins, which extend
from Wales to the Ukraine.
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