WA-27I-P, EXMOUTH SUB-BASIN—INTEGRATED PROSPECTIVITY EVALUATION

Abstract

Permit WA-271-P in the southern Exmouth Sub-basin was initially gazetted as W96–20 in the 1996 gazettal round.

It was recognised at an early stage that fluids found in Novara-1 (14° API oil), Pyrenees-1 and Macedon-1 (19° API oil and gas) made economic viability of traditional Barrow Group prospects in WA-271-P problematic and dependant upon the accurate prediction of reservoir development and fluid type.

After award, Woodside embarked upon an intensive data acquisition program that included 800 km2 3D, 1,600 km 2D seismic, and 34,000 line km of aeromagnetic data. The integration of this data was completed in the latter part of 1998. The evaluation of the exploration 3D survey in the north eastern portion of the permit included volume interpretation and 3D visualisation, the results of which were integrated with an aeromagnetic and gravity study of the permit. The resultant interpretation clearly defined fault patterns and confidently identified and distinguished seismic anomalies caused by fluid effects from those generated by igneous bodies. This interpretation was supported by the application of quantitative interpretation techniques to Near, Full, Far stacks and DMO gathers with the knowledge then extrapolated to the regional 2D seismic grid beyond the 3D survey area.

Environmental risk awareness and contingency planning formed an integral part of the early work within the permit. A metocean survey and spill modelling study were conducted leading to the production of a Resource Atlas. The results of the environmental studies were incorporated into the timing of exploration activities to minimise any potential impact on the environment.

In summary, a focussed and multidisciplinary approach to the evaluation of the prospectivity of the permit was achieved through an integrated work flow. This has resulted in an attractive portfolio of prospects and leads from a number of play fairways, improved risk assessment, and the development of new plays within the permit, including both the traditional Barrow Group plays, and Jurassic and Triassic deep water plays. This approach has added considerable value to the permit by introducing new technologies and successfully managing risk with old play types.

The first prospect drilled in the permit in December 1998, Vincent–1, was an oil and gas discovery.