Areas W07-5, W07-6 and W07-7
Caswell Sub-basin, Browse Basin
Browse Basin Geology
Hydrocarbon Habitat
The Browse Basin is one of Australia’s most hydrocarbon-rich basins. It has estimated reserves of 13.6 MMbbls (2.2 GL) of oil, 25.9 TCF (733.0 BCM) of gas, 438.2 MMbbls (69.7 GL) of LPG and 543.4 MMbbls (86.4 GL) of condensate as at January 2005 (Geoscience Australia, 2004). This represents more than half of Australia’s total hydrocarbon production. The most significant hydrocarbon fields of the Browse Basin occur in the Caswell Sub-basin;
- Scott Reef (Torosa) 11.5 TCF gas, 121 MMbbls condensate (DOIR, 2005),
- Brecknock 5.3 TCF gas, 109 MMbbls condensate (DOIR, 2005),
- Brecknock South (Calliance) 4.0 TCF gas, 87 MMbbls condensate (DOIR, 2005),
- Brewster area, Ichthys 9.5 TCF gas, 312 MMbbls condensate (INPEX, 2006), and
- Crux 1.3 TCF gas, 48 MMbbls condensate (Nexus investor update, March 2006).
During late 2006–07 several appraisal wells were drilled; Brecknock 3, Torosa 1, 2 and 3, and Prelude 1, 1A. Brecknock 3 reached a total depth (TD) of 3,948 m, to appraise the Early to Middle Jurassic Plover Formation reservoir. It intersected a 48.5 m gross gas column. A second hydrocarbon bearing zone was intersected in the Late Cretaceous overburden with an 8.7 m gross gas column (Woodside investor update, November 2006). Torosa 3 reached TD in November 2006, but details have not been released by the operator (Woodside) at the time of publication, and Torosa 2 is currently drilling (January 2007). Prelude 1 was terminated due to a severed drill string at 1385 m, and a follow-up well, Prelude 1A, is currently being drilled (January 2007).