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ABSTRACT: Petroleum Geology of Shallow-Water Basins Around Viti Levu, Fiji

Howard Johnson

From 1980 to 1982 five deep wells were drilled in the mainly shallow-water sedimentary basins around Viti Levu, Fiji. All the wells missed their limestone targets and were dry. There remain reasonable prospects, however, as there are numerous potential trapping styles, including reef-like anomalies. There are also indications from offshore geochemical anomalies that thermogenic hydrocarbons have been generated, and a possible "flat-spot" amplitude anomaly on seismic data may indicate trapped hydrocarbons. However, the major doubt concerning prospectivity is the availability of adequate source-rocks.

The Bligh Water Basin, north of Viti Levu, is interpreted as a late Miocene and younger strike-slip intra-arc basin that overlies a more extensive late Oligocene to late Miocene forearc basin. Total sedimentary thickness is unproven, but about 3 km of late Miocene and younger strata occurs locally. East-northeast-trending wrench faults and folds relate to the breakup of the outer Melanesian Arc in the late Miocene. Since the Pliocene extensional tectonism has been dominant.

Total sedimentary thickness in the Bad Waters basin, east of Viti Levu, is also unproven, but about 2 km of late Miocene to Recent strata locally occurs associated with northwest-trending late Pliocene extensional half-grabens. Pliocene rifting probably relates to regional extension associated with opening of the Lau basin.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990