The Simpson Basin is an Triassic basin.
The basin overlies Palaeozoic and older basins and is overlain by the Eromanga Basin (Jurassic to Cretaceous).
|Area in South Australia||50 000 km2 (19 300 sq miles)|
|Depth to target zone||2000-2600m|
|Thickness||Up to 300m|
|Hydrocarbon shows||Peera Peera Formation (shows in 5 wells)|
|First commercial discovery||None|
|Undiscovered resources (50%)||Not determined|
|Reservoirs||Meandering fluvial sandstone|
|Regional structure||N-S faulted anticlines in sag basin|
|Seals||Lacustrine and overbank sediments|
|Source rocks||Underlying Pedrika Basin siltstone and shale; Peera Peera Formation siltstone and shale|
|Number of wells||6|
Seismic line km
During the Triassic, the western Pedirka Basin area remained elevated and was eroded, while the eastern portion subsided to form a depocentre, the Poolowanna Trough. Regional uplift and erosion terminated deposition in the Simpson Basin at the end of the Early to Middle Triassic. The main episode of structuring occurred in the Early Tertiary, when E–W compression produced major meridional faulted anticlines.
A seismic survey in 1971 revealed an eastward thickening sediment package between the eastern Pedirka Basin and the Eromanga Basin. The postulated Triassic age for these sediments was confirmed when Poolowanna 1 recovered oil from this sequence in 1977. Six petroleum wells have penetrated the basin and over 11 000 km of seismic acquired in the 1970s and 1980s by Delhi–Santos. The area was relinquished in 1989–90. A number of licence applications are current.
Walkandi Formation consists of interbedded shale, siltstone and minor sandstone redbeds deposited in a shallow ephemeral lacustrine environment. The unit correlates with the Tinchoo Formation of the Cooper Basin to the east. Peera Peera Formation consists of grey shale and siltstone at the base with minor thin sandstone and coal, a fining upward sandy middle unit and a black, silty highly carbonaceous shale at the top — reflecting deposition on a floodplain crossed by meandering fluvial streams with lacustrine development. It is correlated with the Cuddapan Formation of the Cooper Basin region.
The oxidised nature of the Walkandi Formation redbeds downgrades source potential. However, the overlying Peera Peera Formation is rich in organic matter (TOC up to 5%) and should be oil mature in the Poolowanna Trough. The Peera Peera Formation is considered to be gas-prone with modest oil yields.
Potential trapping mechanisms are dominantly structural (faulted anticlines).
There is no estimate of undiscovered resources.
There are no current projects.
Five PELs are held by Tri-Star Energy Company or their subsidiaries. Licence activity in the previous years are discussed in Exploration and development, and Figure 4 above shows the licence status at the time of publication. For more information on current licences please refer to Holders of Petroleum and Geothermal Tenements in SA information sheet
For more information, contact:
Energy Resources Division
+61 8 8429 2455