Perth Basin

The Perth Basin is a large basin of approximately 174,000 km2 that encompasses both onshore and offshore parts of south-western Western Australia. The basin extends about 1300 km from south of Perth to its northern tip offshore from Carnarvon. 

History

The first major exploration phase in the Perth Basin began with drilling by the BMR and WAPET in the late 1950’s and early 1960’s. WAPET discovered the Yardarino, Dongara, Mount Horner and Mondarra fields onshore in the mid-1960’s. The large Dongara oil and gas field commenced production in 1971. Further exploration resulted in discoveries onshore between 1980 and 2014 with Waitsia being the largest onshore field and most recent discovery. In the offshore regions there have been several phases of exploration with Cliff Head (2001) being the only offshore commercial discovery to date despite numerous offshore wells with oil and gas shows. The Waitsia discovery in 2014 has opened up additional deeper targets and prospectivity onshore. 

Geology

The Perth basin is a Silurian to Recent basin with a complex structural history and at least seven major basin phases. The basin features several deep depocentres with a maximum sediment thickness of 15000 m. Perth Basin strata feature a wide range of depositional environments including alluvial, fluvial, glacially-influenced, lacustrine, deltaic and marine. To the east the basin is bounded by the Darling Fault which is a major crustal-scale feature separating Archean-Proterozoic basement of the Yilgarn Craton from the Perth Basin sedimentary sequences. In the onshore regions most commercial fields produce from Permian-aged sandstone reservoirs although time-equivalent carbonate facies also form reservoirs in places. Oil is generally thought to be sourced by marine shales of the Early Triassic Kockatea Formation whilst gas is sourced from multiple carbonaceous shales and coaly sequences of Permian, Triassic and Jurassic age. Two of the major reservoir units are the Dongara Sandstone (oil and gas) and the Kingia Sandstone (gas).