Exploration in the offshore northern Carnarvon Basin during the last two decades has resulted in a number of major oil and gas discoveries. Recent discoveries in the Dampier (di Toro, 1994; Delfos, 1994), Exmouth (Bauer et al., 1994; Lawry & Carter, 1994; Mitchelmore & Smith, 1994) and Barrow (Beacher et al., 1994; Sit et al., 1994) sub-basins ensure that exploration activity is likely to remain high in these areas for the near future. However, some of these discoveries have been small fields or individual wells with residual oil columns, indicating that still greater quantities of hydrocarbons have escaped from the traps. Recent work on oil-filled fluid inclusions (Lisk & Eadington, 1994) indicates that the loss of hydrocarbons from pre-Cretaceous reservoirs and traps occurred during the past 20 million years, beginning in the Miocene. These hydrocarbons may have been lost, but could potentially have been trapped in younger Cretaceous and Tertiary reservoirs. The Carnarvon Cretaceousflertiary Tie study proposes to address this issue by collecting and interpreting a regional high-resolution seismic survey, within the broad structural and tectonic framework provided by the Continental Margins Program Northwest Shelf Project. The main objectives are: 1) construction of a regional, sequence-based chronostratigraphic framework for the Cretaceous and Tertiary within which the occurrence and distribution of potential seal and reservoir facies may be analyzed and predicted; 2) assessment of the post-Valanginian fault reactivation history of the northern Carnarvon Basin and the implications for: (a) the migration of hydrocarbons from pre-Cretaceous traps and (b) the integrity of potential Cretaceous and Tertiary seals; 3) determination of the probability of secondary migration and entrapment of hydrocarbons within Cretaceous and Tertiary strata. Approximately 4240 krn of high-resolution seismic data has been proposed for acquisition by AGSO's RV Rig Seismic. The data set will comprise 23 seismic lines tying 107 wells in the Exrnouth, Barrow, Dampier and Beagle Sub-basins. These data will tie with and complement the deep-seismic grid previously acquired by AGSO in the Carnarvon Basin. The seismic survey will be acquired using the latest high-resolution seismic technology. Data will be recorded using bubble-free GI air guns and with the following parameters: 3000m streamer; 12.5m group interval, 18.75m shot interval, recording frequency bandwidth of 4- 180Hz; 2ms sample interval; 5.5 second record length; and 80-fold CDP multiplicity. The program layout includes 5 strike lines linking the Exrnouth, Barrow, Dampier and Beagle subbasins and 18 dip lines orthogonal to the principal Mesozoic sub-basin fault systems.

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The quality, quantity and distribution of Australia's convetional petroleum resources are largely controlled by the geoloigcal evolution of its marginal basins formed during Gondwana break-up

Three economic (1 oil and gas/condensate, 1 gas/condensate, and 1 gas) and fourteen uneconomic (6 oil, 7 gas, and 1 oil/gas) petroleum accumulations have been discovered since 1963 in the Amadeus Basin of central Australia. The petroleum in the Amadeus Basin mainly occupies the structural, fold- related traps within the Upper Proterozoic to Upper Ordovician marine to marginal marine clastic and evaporitic sequences. It is believed to be of algal/bacterial origin. The API gravity ranges from 18 to 54o for crude oils, and from 52 to 64o for condensates; gases are dry and wet. The basin's estimated petroleum resources as at 31 December 1985 comprise 5.74 x 106m3 of oil, 1.53 x 106m3 of natural-gas liquids, and 14.93 x 109m3 of sales gas. Production from Mereenie (oil) and Palm Valley (gas/condensate) accumulations commenced during 1984. Up to 31 December 1985 the cumulative production from the basin stood at 156.3 x 103m3 of oil and condensate, and 44.0 x 106m3 of sales gas. The gas/condensate is transported 146 km to Alice Springs through a 20-cm-diameter pipeline; the oil is transported 269 km to Alice Springs through a 20cm pipeline and from there by rail tankers to Adelaide refinery. As from February 1987 gas from Palm Valley will also be transported to Darwin via a 1537-km pipeline of 35.3 cm diameter.

The Adavale Basin, in south-central Queensland, contains two dry gas accumulations, Gilmore and Log Creek, discovered in 1964 and 1965. The accumulations occupy fold-related traps in Middle Devonian clastic rocks of the Log Creek Formation and the Lissoy Sandstone. The basin's estimated initial recoverable reserves as at 31 December 1986 comprised 589 x 106 m3 (20.8 x 109 ft3) of sales gas, all in the Gilmore accumulation. The Gilmore gas accumulation was declared economic in August 1987, and gas production is expected to commence in early 1989. Production so far has comprised 10.4 x 106 m3 (366 x 106 ft3) of raw gas, used in the drilling of nearby extension wells.