The Stansbury Basin is an Early - Middle Cambrian basin.
The prospective area of the Stansbury Basin lies mainly beneath Gulf St Vincent and southern Yorke Peninsula.
|Age||Early - Middle Cambrian|
|Area in South Australia||15 000 km2 (5790 sq miles)|
|Depth to target zone||600-2500m|
|Thickness||Up to 1500m|
|Hydrocarbon shows||Trace gas on DST, trace oil reported in core|
|First commercial discovery||None|
|Undiscovered resources (50%)||Not determined|
|Basin type||Extensional; deformed by marginal collision|
|Depositional setting||Marine shelf-ramp-basin|
|Regional structure||Anticlines on stable nucleas boredered by thrust-zones|
|Seals||Redbeds, micritic limestone, evaporite|
|Source rocks||Marine black shale|
|Number of wells||6 petroleum, 5 stratigraphic, >20 deep mineral drillholes|
Seismic line km
|4753 2D offshore, 625 2D onshore|
In the western Stansbury Basin, Early Cambrian basal sand and marine shelf carbonate onlap the Gawler Craton and pass east into a ramp–basin setting which may have evolved into a foreland trough (Kanmantoo Trough). Structures beneath Gulf St Vincent are chiefly broad, low-amplitude anticlines.
On Yorke Peninsula, where previous petroleum exploration was centred, drilling was mainly in complex fault-block mosaics associated with the Pine Point Fault Zone. This zone was tectonically active during the Early Cambrian resulting in ‘bald-heading’ of some structures, but the principal deformation (collision orogeny) took place in the Middle–Late Cambrian on the eastern and southern structural margins of the basin. The original depositional area was much more extensive to the east and south, and is explored as a mineral province because of its high metamorphic grade and structural complexity.
Glacial erosion in the Late Carboniferous was followed by deposition of up to 2000 m of Permian (Troubridge Basin) and Tertiary sediments. A final compressional event in Tertiary to Recent time reactivated many Delamerian reverse faults along the platform margin.
PEL 73 was granted to David Schuette in 2000. Gravestock 1 exploration well was drilled in February–March 2007 by Austin Exploration in PEL 73 in the Stansbury Basin, but was plugged and abandoned. The well was named to honour the late Dr David Gravestock — former Principal Petroleum Geologist for the South Australian Department of Mines and Energy. Dr Gravestock played a leading role in researching the state’s petroleum exploration potential, geology and Cambrian biostratigraphy over many years, until his untimely death in 1999. PEL 73 was surrendered on 2011.
Differential uplift adjacent to the Gawler Craton was accompanied by foundering of the sea floor and initiation of the Kanmantoo Trough which arcs south and west from the Mt Lofty Ranges to Kangaroo Island. The Kangarooian Movements signify renewed rapid extension, creating space to accommodate great volumes of siliciclastics transported from a southern source. An alternative view suggests that Kanmantoo Trough sediments are older than depicted in Figure 4 and a younger foreland trough sequence accumulated rapidly as a result of convergence of the Delamerian Orogen.
Carbonate and evaporite accumulated in the Minlaton Formation, and two major marine flooding events are represented on Yorke Peninsula by three third order sequences, namely Є2.2 (Ramsay Limestone – Corrodgery Formation), Є2.3 (Stansbury Limestone – Moonan Formation) and Є3.1 (uppermost Moonan and Coobowie Limestone). Sequences Є2.2 and Є2.3 are interpreted to correlate with the major basinal successions represented by the Talisker Calc-siltstone – Karinya Shale and Balquhidder Formation on Fleurieu Peninsula. Alternatively the Talisker, Karinya and Balquhidder could be older. The Coobowie Limestone is of Middle Cambrian age based on the first appearance of the trilobite Pagetia. Redbeds of the Yuruga Formation (Є3.2) are the youngest Cambrian strata preserved beneath the Permian unconformity on Yorke Peninsula.
Tertiary sediments of the overlying St Vincent Basin accumulated in mildly compressional foreland troughs following the separation of Australia and Antarctica. Depositional patterns were strongly controlled by older structural trends. A maximum thickness of 600 m of Tertiary and Quaternary sediments has been recorded.
Dolomitised limestone of the Kulpara Formation constitutes the principal reservoir and reaches 500 m in thickness. Core porosity ranges up to 13% and permeability reaches 340 mD. Brine recovered on test ranges from 13 000 to 157 000 ppm sodium chloride in Stansbury West 1, suggesting connate pore water and unbreached structures still exist.
Porosity is also indicated on wireline logs in the Koolywurtie reef complex which is up to 73 m thick (where not eroded by Minlaton Formation conglomerate), and may have originally extended from Ardrossan to Kangaroo Island, a distance of 100 km or more.
Potential sandstone reservoirs are arkosic with patchy carbonate cement, and porosity in outcrop is generally low. Their thickness (100 m, Winulta; ~350 m, Stokes Bay) justifies consideration as a secondary target, but their stratigraphic position below potential source rocks implies structuring may be necessary to elevate them to a level suitable to trap migrating hydrocarbons. Sands of the upper Moonan Formation (~40 m thick) occur near the Middle Cambrian and may develop as reservoirs at the Є2.3 sequence boundary.
The Kulpara Formation is sealed by thick micritic Parara Limestone. Regional seal was once provided by thick redbeds of the Yuruga Formation, but Permian glacial topography may have locally breached some traps. Notably, the oil shows in Minlaton 1 were in basal Permian strata.
Potential sandstone reservoirs on Fleurieu Peninsula (basal Sellick Hill Formation), Kangaroo Island (Stokes Bay Sandstone) and extensions beneath western Gulf St Vincent may pass eastward into impermeable shales which act as semi-regional seals.
Structures with trap potential are fault-dependent and are mainly concentrated in the NNE striking Pine Point Fault Zone adjacent to the east coast of Yorke Peninsula. Simple domes may underlie northern Gulf St Vincent and the north Adelaide Plains near Dublin, and may be suitable for gas storage.
There is no estimate of undiscovered resources.
A review of Stansbury and Arrowie basins biostratigraphy was completed by Jago et al. (2002). Use this link to view the report.
A number of National Parks and Wildlife reserves overlie the
However, exploration access is not restricted in the prospective areas.
Figure 5 shows the licence status at the time of publication. Use this link for further information on holders of petroleum tenements in South Australia.
There are no licences current over the Stansbury basin.
Flöttmann T, Haines PW, Cockshell CD and Preiss WV, 1998. Reassessment of the seismic stratigraphy of the early Palaeozoic Stansbury Basin, Gulf St Vincent, South Australia. Australian Journal of Earth Sciences, 45:547-557.
Gravestock DI, Alexander E, Demidenko YuE, Esakova NV, Holmer LE, Jago JB, Tian-rui Lin, Melnikova LM, Parkhaev PYu, Rozanov AYu, Ushatinskaya GT, Zang W, Zhegallo EA and Zhuravlev AYu, 2001. The Cambrian biostratigraphy of the Stansbury Basin, South Australia. Russian Academy of Sciences Palaeontological Institute. Transactions, 282.
Haines PW and Flöttmann T, 1998. Delamerian Orogeny and potential foreland sedimentation: a review of age and stratigraphic constraints. Australian Journal of Earth Sciences, 45:559-570.
Jago JB and Moore PS eds, 1990. The evolution of a Late Precambrian – early Palaeozoic rift complex: the Adelaide Geosyncline. Geological Society of Australia. Special Publication, 16.
Jago JB, Sun X and Zang W, 2002. Correlation within early Palaeozoic basins of eastern South Australia. South Australia. Department of Primary Industries and Resources. Report Book, 2002/00033.
Sprigg RC, 1961. Oil and gas possibilities of the St Vincent Gulf graben. APEA Journal, 1:71-88.
Stuart WJ and von Sanden AT, 1972. Palaeozoic history of the St Vincent Gulf region, South Australia. APEA Journal, 12:9-16.
Teasdale J, Pryer L, Etheridge M, Romine K, Stuart-Smith P, Cowan J, Loutit T, Vizy J and Henley P, 2001. Western Stansbury Basin SEEBASE Project. SRK Consulting report, SRK Project Code: PI12. South Australia. Department of Primary Industries and Resources. Open file Envelope, 9889 (unpublished).
For more information, contact:
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