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ABSTRACT: Petroleum Prospectivity Along the Outer Melanesian Arcs, SW Pacific

FALVEY, DAVID A., Bureau of Mineral Resources, Canberra, Australian Captial Territory, Australia, and PATRICK J. COLEMAN, Geology Department, University of Western Australia, Nedlands, Western Australia, Australia

The Outer Melanesian arc system includes the arc segments of the Solomon Islands (including New Ireland and Bougainville), New Hebrides (Vanuatu), Fiji Platform and Tonga, all of which have large, old (Tertiary) basins that contain up to 7 km of sediment. The few wildcat petroleum wells drilled in these basins, off Bougainville (Solomons), Bligh Water (Fiji), and Tongatapu (Tonga) have all been unsuccessful. These results, along with interpretations of marine geophysical data collected under the Australian-New Zealand-United

States "Tripartite" Geoscience Program during the 1980s, suggest that the thick volcaniclastic forearc or intra-arc depocenters have low potential. Instead, the areas marginal to these depocenters and adjacent to major islands may have significant potential. On such basin edges, the complex tectonic history will have favored the growth of marginal reef systems bordered by deep graben and half-graben basins. The marginal marine and coastal environments have been, in large part, intensely productive of organic material favorable to petroleum generation. Stripping mechanisms, such as cyclones and tsunamis, harvest this material and deposit it in the deep basins adjacent to reef bodies, with subsequent maturation and migration into reefal reservoirs. This marginal play has not been tested Promising shallow-water target areas include: in northeastern Papua New Guinea--shore edge of New Ireland basin and nearshore borders to the Queen Emma and Bougainville basins; in Solomon Islands--Manning Strait, eastern Iron Bottom Sound and Mbokokimbo basin; in Vanuatu--southwest Vanikolo basin, western East Santo basin; in Fiji--shoreward Bligh basin; in Tonga / Eua Channel area.

 

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)