Exploration History

The onshore parts of the Gippsland and Taranaki basins have long histories of exploration. Shallow drilling in Taranaki started in 1866 adjacent to seepages (Katz, 1968) and in Gippsland in 1924 after the indications of oil in water wells (Colman, 1976). Significant production took place onshore in both basins before

Ontario Sedimentary Basins
Fig. 6.2. Distribution of the sedimentary basins of the southwestern Pacific during the Upper Cretaceous when the breakup of Gondwana began (after Grindley and Davey, 1982). Basin identification is given in Fig. 6.1.

exploration moved offshore in Gippsland in 1951 and in Taranaki in 1965. Subsequent major oil and gas finds have vastly increased the reserves of both basins and encouraged further exploration. The present levels of knowledge of the geology of these basins and of the hydrocarbon sources and reservoirs are considerable (Threlfall et al., 1976; Shibaoka et al., 1978; Thomas, 1982; Cook, 1988; King and Robinson, 1988). The basins south of 45°S, which are entirely offshore, have much lower levels of exploration.

All the basins of the Campbell Plateau have at least reconnaissance seismic data. The Great South Basin has had 8 wells drilled in it and the Canterbury Basin 4 wells since 1970. Subcommercial finds of gas and traces of oil have been reported from several of these wells (Katz and Herzer, 1986). These have encouraged explorers and helped focus on areas with better potential for further work. The Solander Basin has also been drilled with 2 wells since 1975 but no hydrocarbons were recorded. The other basins of the Campbell Plateau (Campbell Basin and Pukaki Basin) have yet to be drilled, although they have been defined by good reconnaissance seismic and the Deep Sea Drilling Project (DSDP) site 277 (Anderton et al., 1982).

Under the Antarctic Treaty, no commercial exploration has been carried out in the Antarctic or on its adjacent continental shelf, although scientific work carried out in the region has produced enough regional seismic data to define the basins of the Ross Sea (Davey et al., 1982; Davey, 1985; Hinz and Kristoffersen, 1987).

When combined with the drilling of the DSDP, McMurdo Sound Sediment and Tectonic Studies (MSSTS) and Cenozoic Investigations of the western Ross Sea (CIROS) projects in these basins, some ideas of the sediments of the basin are obtained. The minor hydrocarbon shows during the drilling of DSDP holes 271-273 (Mclver, 1975) together with the residual oil show in CIROS-1 (Cook and Woolhouse, 1988) have caused speculation about the presence of commercial hydrocarbon accumulations especially in the preliminary discussions for the minerals regime to be attached to the Antarctic Treaty.

The Bellingshausen area has had no exploration and less scientific work than the Ross Sea. No DSDP drilling has taken place on this shelf area. DSDP holes 323 and 445 were drilled in the deeper area beyond the shelf. Only the very limited seismic coverage allows some definition of the sediments present (Davey, 1985; Hinz and Kristoffersen, 1987).

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