ABSTRACT: Petroleum Prospectivity of the Bligh Water and Bau Waters Basins, Fiji

JOHNSON, HOWARD, British Geological Survey, Edinburgh, United Kingdom

The intra-arc Bligh Water and Bau Waters Basins which underlie the shelf seas surrounding much of Viti Levu, Fiji, have attracted commercial petroleum exploration interest since 1969. Exploration targets in the five deep wells in these basins were Lower to Middle Miocene reef limestones similar to those that crop out on Viti Levu, but these targets were not intersected by the wells which were all dry.

Recent interpretations of the newly released, and extensive, seismic coverage from the Bligh Water and Bau Waters Basins, together with well data and the geology of the Fiji islands, suggest that the basins are filled with up to about 4 km of Upper Miocene and younger deposits which are dominantly composed of volcaniclastics. Intra-Late Miocene, Early Pliocene, and Late Pliocene seismic markers in the basins locally correspond to significant unconformities and are believed to be related to compressional and extensional tectonic pulses associated with the strike-slip pull-apart and rifting of the Fiji Platform and the growth of the surrounding back-arc basins.

Mid-Miocene and older sedimentary rocks drilled in the deep wells underlie the Bligh Water and Bau Waters Basins, but are generally

not resolved on seismic data. Anomalous amounts of pentane in Bligh Water sea bed sediments suggest that some thermogenic hydrocarbons have been generated, and models have been proposed postulating organic source materials derived from ancient marginal marine and reef environments. Reprocessing of the Bligh Water and Bau Waters seismic data is recommended to evaluate the potential for Lower to Mid-Miocene reef plays. Upper Miocene and Pliocene structural and stratigraphic traps have been identified and coarse volcaniclastics and limestones form potential exploration targets.

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