Source rocks of Oligocene, Miocene and Pliocene age are exposed onshore in Fiji and have been encountered by drilling in the offshore basins. An oil seep in Bligh Water Basin and oil and gas shows in wells provide evidence that hydrocarbons have been generated in the basins. Modelling studies indicate peak oil generation to be at about 2.6km below sea floor. Miocene and Pliocene reefal limestones form spectacular outcrops in Fiji and represent the best potential reservoirs. Reefs of the same age have been identified on seismic data from the offshore basins and represent attractive targets for exploration.
Common forms are reefal mounds and prograded platforms.
Over twenty structural reefal traps have been identified on seismic lines in the Late Miocene and Pliocene sequences, mostly in Bligh Water Basin. If structural-stratigraphic trapping occurs, recoverable reserves could increase to over 1 billion barrels of oil per structure. There is considerable scope for more reefal structures in the deeper Oligocene-Middle Miocene interval which cannot be resolved on the existing seismic data, and in areas where seismic coverage is sparse. Limestone turbidite lobes have also been identified on seismic data. These constitute a secondary play and may contain estimated recoverable reserves of 100-200 mmbo per structure.