INTRODUCTION

In 2006, the Prime Minister announced A$134 million in Commonwealth Government funding for Geoscience Australia as part of the Australian Government's Energy Security Initiative. The funding extends from 2006 until 2011 and includes A$76.4 million to expand Geoscience Australia's Offshore Energy Security Program to identify new hydrocarbon provinces.

As part of this program, a new tectono-stratigraphic and petroleum systems study has been carried out in the Vlaming Sub-basin on Australia's southwest continental margin. The study has included revising the biostratigraphy for key wells, interpreting new and reprocessed seismic data, a new geochemical assessment of key source rock intervals and recovered liquid petroleum, structural restoration and 3D burial history modelling. Results have significantly improved our understanding of the Vlaming Sub-basin's evolution and provide a basis for future exploration. New exploration opportunities in the southern Vlaming Sub-basin are open to explorers through the Commonwealth Government's 2008 Acreage Release.

ACREAGE RELEASE AREAS WA08-23 AND WA08-24, VLAMING SUB-BASIN, PERTH BASIN

The Vlaming Sub-basin is an elongate, north-south trending depocentre that lies within the continental shelf and upper slope (0-1000 m water depth) in the offshore southern Perth Basin (Figure 1). Acreage release areas WA08-23 and WA08-24 are located in the southern part of the basin, which has had limited previous exploration.

During initial exploration activity in the 1970s to early 1980s, reasonable 2D seismic coverage was acquired over most of the sub-basin and 16 wells were drilled. However, except for a non-commercial oil discovery at Gage Roads 1, all wells drilled on potential 4-way closure prospects were unsuccessful. This halted exploration activity for almost two decades. Subsequent analysis has shown that exploration failure in the Vlaming Sub-basin was due to inadequate seismic coverage and therefore poor structural definition of prospects (Miyazaki et al., 1996).

An uptake of acreage in the Vlaming Sub-basin in 2005 started a new round of exploration activity in the northern and central parts of the sub-basin. At present, NEXUS holds one permit (WA-368-P) and ROC OIL two permits (WA-381-P and WA-382-P). Both companies are in the process of acquiring or have planned to acquire new seismic data with commitments drill one well in each permit. In 2008 two new areas are being released in the southern Vlaming Sub-basin (WA08-23 and WA08-24). Since the non-commercial oil discovery at Gage Roads 1, exploration activity has been focused in the northern part of the sub-basin. The southern part is more structurally complex and has a higher proportion of sandstones in its syn-rift section. Only two wells have been drilled in this area: Sugarloaf 1 (1971) and Felix 1 (1998), both failing to find any indications of hydrocarbon. Seismic coverage in this part of the basin is relatively sparse (Figure 2) and older vintages of seismic data tend to be of poor quality and low resolution. However, active petroleum systems present in the northern Vlaming Sub-basin are likely to extend to the south where there is potential for hydrocarbon accumulations.