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Introducing the Untested Sub-Salt Play in the Officer Basin, South Australia*
Peter J. Boult1,2, Clerk M. Petrick1, Vicki Stamoulis2, and Kerry Deller1
Search and Discovery Article #10096 (2006)
Posted January 28, 2006
*Modified from extended abstract prepared for presentation at AAPG International Conference, Paris, France, September 11-14, 2005
1Australian School of Petroleum, University of Adelaide, Adelaide, Australia ([email protected])
2PIRSA, Adelaide, Australia
The Neoproterozoic–Devonian eastern Officer Basin, South Australia (Figure 1), has the potential to contain several very large oil fields within horsts capped by thick salt (Boult and Rankin, 2004). Oil shows are common in mineral wells and some have been correlated to sub-salt source rocks. Excellent quality reservoirs are proven in nearby wells (>20% phi, >1 darcy) and abundant salt implies long-term preservation is feasible. Target depths are less than 1 second TWT.
The stable Murnaroo platform, which is adjacent to the Munyarai Trough (Figure 2) containing up to 10 km of sediment, comprises over 1 km of undrilled section, including ~500 m of continuous salt canopy above the aeolian Pindyin Sandstone. Cambrian generation and migration occurred after the development of Neoproterozoic–Cambrian traps. Transpression and likely breaching of traps during the Carboniferous Alice Springs Orogeny is confined to north of the Birksgate Coober-Pedy strucutural corridor, which forms the boundary between the platform and trough (Figure 3).
Magnetotelluric methods are proving to be an effective and cheap method for mapping salt onshore due to the high resistivity contrast between highly resistive rock salt and surrounding very conductive saline saturated sediments. Salt diapirism is confined to the deeper parts of the basin and is controlled by basement structure. Its movement was initiated during the late Proterozoic, where infill canyoning events are mapped, and continues today where movement can be mapped on satellite images of the earth’s surface.