ABSTRACT: Hydrocarbon Prospectivity of the Island Intra-Arc Basins of Vanuatu and Solomon Islands

RODD, J., and W. BARCLAY, South Pacific Applied Geoscience, Suva, Fiji

The intra-arc basins contain sediment thicknesses in excess of 5 ranging from Oligocene to Recent. Extensive shallow water areas in less than 1 km water depth occur around the basin margins within reach of modern production economics and technology.

Oil company exploration occurred in the early 1970s when sparsely regional single and multi-channel seismic was acquired. This activity culminated in the drilling of one well in northern offshore Solomon Islands which proved to be off-target.

Since then over 7,500 km of good quality multi-channel seismic has been acquired by SOPAC-coordinated development and research organization acting on behalf of the respective governments. Two stratigraphic holes were also drilled in the Vanuatu intra-arc basin as part of the ODP program in 1990. These new data form the basis of this re-evaluation of the hydrocarbon prospectivity in the area.

The intra-arc basins were continuous with the forearc basins of Tonga and Fiji until Late Miocene times. Thus, it is likely that the same source rocks which give rise to oil seeps Tonga may also be present in the intra-arc basins of Vanuatu and Solomon Islands. Oil charge is further supported by source rock maturity modeling which indicate that at present the top of the oil window is at 2-3 km.

Play concepts based on interpretation of the new seismic include shallow basin margin reefal mounds sealed by pelagic shales, and submarine fan lobs and channel deposits sealed by basinal shales and/or volcaniclastics, and tilted fault blocks.

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