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Regional Geology of the Southern Carnarvon Basin

The Southern Carnarvon Basin is a large (192 000 km²) predominantly Paleozoic sedimentary basin covering onshore and offshore regions of north-western Western Australia. It lies to the south of the Mesozoic Northern Carnarvon Basin, Australia’s premier oil and gas producing basin. The Southern Carnarvon Basin comprises the Gascoyne, Merlinleigh and Byro sub-basins and the Bernier Platform (Figure 1 and Figure 2). Of these, the Bernier Platform and western Gascoyne Sub-basin lie offshore. The offshore part of the Gascoyne Sub-basin lies mostly in shallow water (50–200 m), whereas the Bernier Platform is in much deeper water (200–2000 m). The offshore part of the Southern Carnarvon Basin covers an area of approximately 95 000 km².

Petroleum exploration of the Southern Carnarvon Basin began with the discovery of Rough Range oil field in 1953. It was followed by two decades of regional mapping and unsuccessful drilling. By the mid-1970s, petroleum discoveries in the adjacent Northern Carnarvon Basin attracted exploration focus and exploration in the Southern Carnarvon Basin almost ceased. Systematic mapping of the onshore basin by the Geological Survey of Western Australia and offshore exploration by industry in the 1990s demonstrated the potential prospectivity of this underexplored region. To date, 76 onshore (including 57 stratigraphic tests) and only two offshore wells (Pendock 1a and Edel 1; Figure 1) have been drilled in the Southern Carnarvon Basin. No offshore fields or accumulations have yet been discovered. The Southern Carnarvon Basin is close to infrastructure at Carnarvon which connects to the West Australian pipeline network (Figure 1).

Note: the full set of high resolution figures are available via the link at the bottom of this page.

Figure 2: Structural elements map for the Southern Carnarvon Basin showing the location of petroleum wells and location of cross-sections in Figures 5, 6, 7 and 11.

Figure 3: Bouguer gravity image of the Southern Carnarvon Basin showing the correlation between gravity anomalies and major depocentres within the basin. Tectonic elements of the Southern Carnarvon Basin based on current interpretation and compilation from Hocking et al (1987), Lockwood and D'ercole (2004) and Woodside (2003b, 2003c).

Figure 4: Geological cross-sections of the main structural provinces within the Southern Carnarvon Basin (modified from Hocking et al, 1987). See Figure 2 for location of cross-sections.

Figure 5: Seismic line gpctr-93-0405 showing tectonic relationship between the Northern and Southern Carnarvon basins. Line location shown on Figure 2.

Figure 6: GA-acquired seismic line s310/42 across boundary between Exmouth Sub-basin and Gascoyne Sub-basin, showing structural architecture below regional Cretaceous unconformity. Line location shown on Figure 2.

Figure 7: Seismic line (wg98ct-4) across the boundary between the Bernier Platform and the Mesozoic depocentre of the southern Exmouth Sub-basin. Line location shown on Figure 2.

Figure 8: Generalised stratigraphy of the Southern Carnarvon Basin (after Gradstein et al, 2004 and Ogg et al, 2008).

Figure 9: Map showing seismic data coverage in the Southern Carnarvon Basin.

Figure 10: Stratigraphic chart for the Southern Carnarvon Basin showing petroleum systems elements and possible play types (Geologic Time Scale after Gradstein et al, 2004 and Ogg et al, 2008).

Figure 11: Seismic line (Cuvier seismic survey, line 92m-126) across the northern Bernier Platform showing potential Paleozoic plays. 1 - Miocene anticline, 2 - Paleozoic horst block, 3 - Devonian reef (modified from Geary, G., 1994). Location of the seismic line is shown on Figure 2.

Figure 12: Generalised cross-section showing conceptual plays across the Southern Carnarvon Basin and southernmost Northern Carnarvon Basin. Source rock intervals: SR1 - Coburn Formation, SR2 - Gneudna Formation, SR3 - Locker Shale, SR4 - lacustrine shales of Mungaroo Formation, SR5 - Dingo Formation

Figure 13: Map showing marine reserves, marine parks, multiple use zones and ecological features in the Southern Carnarvon Basin

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