• Exmouth Sub-basin
• Barrow Sub-basin
• Dampier Sub-basin

Exmouth Sub-basin

At the end of 2001, the Exmouth Sub-basin contained 16 field discoveries and 74 exploration wells with a historical technical success rate of 22% and 8% success rate for fields greater than 20 million boe. The sub-basin is estimated to contain reserves of 1.2 tcf gas, 0 million bbls condensate and 278 million bls oil (Longley et al., 2002).

Recent successful discoveries in the central western part of the sub-basin have provided considerable encouragement for deepwater exploration, although the area has a biodegradation risk.

1947	Beginning of petroleum exploration in the Exmouth area. First exploration lease granted on the North West Cape.
1953	Discovery of oil at Rough Range-1. First well in Australia to flow oil at the surface which stimulated interest in the area and led to further onshore petroleum exploration.
1970-80s	Acquisition of marine seismic data. 1979: Drilling of Resolution-1 and Zeewulf-1 Early 1980s: Drilling of Zeepard-1, Jurabi-1, Vlaming Head-1 and Novara-1
1990s	Discovery of the Griffin (1989), Chinook/Scindian (1990/1992) and Ramilies (1991) oil and gas fields. These fields are reservoired in the Zeepard and Birdrong Formation. Caretta-1 (1991) discovered a 41m gross oil column within the Mardie Greensand, Barrow Group and Dupuy Formation. Leatherback-1 (1991) discovered Triassic oil within a tilted fault block and proved the viability of this play type on the eastern margin of the Northern Carnarvon Basin.
1992-1994	Discovery of top Barrow play on the Alpha Arch and the Macedon/Pyrenees field. This structure, however was first tested by WAPET during 1972 and 1975 with West Murion-1A and the extent of the hydrocarbon accumulation was not recognised and WAPET relinquished the acreage.
1998-2000	Recent discoveries of oil accumulations in central western part of the sub-basin: Vincent-1 (1998), Enfield-1 (1999), Coniston-1 (2000), Laverda-1 (2000); Woodside (operator of WA-191-P) propose to develop the Vincent, Enfield and Laverde accumulations (all reservoired within the Macedon Sandstone, lower Barrow), which collectively have reserves of more than 300 million barrels.

1954	Beginning of exploration in the Barrow area. Discovery of Australia's first flowing oil at Rough Range-1 (1953), Exmouth Sub-basin. Field mapping of Barrow Island discovered a large north-plunging anticline that outcropped on the surface.
1964	Drilling of Barrow-1 after seismic refraction survey.
1968	Exploration turned to the Rankin Platform after the release of BMR's geophysical survey and subsequent recognition of tectonic elements.
1970s	Discovery of the North Rankin Gas field (1971) in the adjacent Dampier Sub-basin. Major hydrocarbon discoveries: West Tryal Rocks-1 (1972) made a gas/condensate discovery in the Triassic Mungaroo Formation; Spar (1976) which encountered gas in the Lower Cretaceous Barrow Group west of Barrow Island; Campbell (1979) recovered gas from the Flag Sandstone to the northeast of the island.
1981	Gorgon was drilled on the Rankin Platform, which penetrated another major gas/condensate accumulation in the Triassic Mungaroo Formation.
Early 1980s	A large number of wells were drilled and resulted in oil discoveries; South Pepper (1982); North Herald (1983), Harriet (1983), Chervil (1983); Outtrim (1984); Saladin (1985).
Late 1980s	Although the number of offshore exploration wells significantly decreased, a number of major discoveries occurred. Rosette (1987) intersected oil within the Flag Sandstone. Yammaderry (1988) and Cowle (1989) intersected oil at 'Top' Barrow in traps associated with the Flinder Fault Zone and Chinook-1 (1989) drilled on the Alpha Arch also intersected oil at 'Top' Barrow level.
1990s	Drilling focused on extending the reserves from existing fields. Roller (1990) and Skate (1991) hydrocarbon accumulations extended known play fairways identified by the Yammaderry and Cowle fields. Sinbad (1990), Tanami (1991), Alkimos (1993), Wonnich (1995) and Agincourt (1996) are all accumulations testing prospects both north and north-east of Barrow Island that target the Early Cretaceous Flag Sandstone. Other wells which targeted similar plays included the East Spar (1993), Nimrod (1996) and John Brookes (1998) gas/condensate and oil fields. The Early Cretaceous Sandstones resulted in the discovery of Crest (1994), Woolybutt (1997), Coaster (1999) and Nasutua (1999). Other significant hydrocarbon accumulations include those encountered in Palaeocene sandstones at Maitland-1 (1992) and within Triassic sandstones at Gypsy-1, Rose-1 and Lee-1 in 1998. The Linda-1 well, located approximately 4 km north-west of the Gipsy/Rose/Lee fields, intersected a 91m gas-condensate column in Jurassic Biggada Sandstones and represented the first purely stratigraphic discovery of significant size in Oxfordian sandstones in the Carnarvon Basin. Tanami-4, located south of Linda-1, encountered an 18.9 metres thick gross oil column at the top of the Flag Sandstone and has been suspended as a future oil producer. Recent drilling west of the Greater Gorgon field has resulted in five significant gas discoveries; Geryon-1, Orthrus-1, Urania-1, Maenad-1 and Io-1 and Janz-1. Wonnich Oil and Gas Field, discovered in 1995, began commercial gas and condensate production in 1999.
2000-2002	A string of recent discoveries have been made in the Harriet area, including the North Alkimos oil and gas discovery.
Early 2001	Simpson, South Plato and Gibson oil discoveries. Apache Energy Ltd has had recent success at the Simpson Field, to the south of Harriet. The discovery well was drilled in February 2001 and production commenced in November 2001 at a rate of 20,000 bpd.

Longley et al., 2002

Dampier Sub-basin

1968	First discovered in the Dampier Sub-basin. Legendre-1, first offshore well drilled.
1970s	Boost in exploration and discovery of numerous gas fields: Discovery of the North Rankin Gas field (1971); Angel and Goodwyn fields; Other smaller discoveries along the Rankin Trend.
1980s	Exploration activity increased. Wilcox, Dixon and Talisman oil and gas discoveries. Mid-late 1980s acquisition of modern seismic enabling comprehensive basin re-evaluation studies. Wanaea field discovered (1989). Cossack field discovered (1990).
1990s	Improvement in sub-surface imaging through 3D seismic acquisition and processing. Many wells were drilled to extend the reserves known from existing fields or discoveries (Yodel-1, Chrysaor-1, Perseus-1 and Dionysus-1 which extended the known gas reserves along the Rankin Trend). Reindeer-1 (1997), Jaubert-1 (1997) and Caribou-1 (1998) drilled on the Legendre Trend to re-evaluate earlier discoveries and test new play concepts. Exploration wells were also drilled throughout the Dampier Sub-basin depocentre and on the eastern margin to test new plays. Wandoo-1 (1991) was the first oil discovery on the Enderby Terrace and Saffron-1 (1994) discovered gas and oil in the Mardie Greensand on the Talisman-Legendre-Rosemary Trend.
1999-2000	Several deep-water wells (water depths greater than 500m) were drilled. Gaea-1 exploration well was drilled south-west of the North Rankin production platform and was the first test of the Parker Terrace directly adjacent to the Goodwyn, Perseus and North Rankin fields. Corvus-1 located 30 km northwest of the Stag oilfield. Iago-1 located 7 km north-northeast of North Tryal Rocks-1. Titania-1 set the record for the deepest water depth (1501 metres) drilled in Australia.

Longley et al., 2002