Amadeus Basin

The Amadeus Basin is exposed over about 170,000 km2 in central Australia. The majority of the basin lies within the Northern Territory (NT), but about 30,000 km2 extends into Western Australia (WA). Whereas the eastern part of the basin is relatively accessible, well studied, and has an existing petroleum industry infrastructure, the western portion is poorly explored and access is difficult. Unsealed highways (Great Central Road and Gary Junction Road) lie along the southern and northern margins of the WA Amadeus Basin, linked near the WA–NT border by the north–south oriented Sandy Blight Junction Track.

Geological setting

Outcropping Heavitree Quartzite in the Western Amadeus Basin
Outcropping Heavitree Quartzite in the Western Amadeus Basin

The Amadeus Basin overlies Paleo- to Mesoproterozoic metamorphic and igneous basement domains of the Arunta Province (north) and Musgrave Province (south), and locally contains up to 14 km of Neoproterozoic and Paleozoic sedimentary rocks. It is overlain to the west by late Paleozoic (Permian) rocks of the Canning Basin. Remnants of a latest Mesoproterozoic sedimentary and volcanic rift phase are also present locally, but by definition are excluded from the Amadeus Basin succession.

The present basin margins are mainly of tectonic origin, the Neoproterozoic component of the Amadeus Basin being one of several remnants of the hypothetical Centralian Superbasin. This is perceived as a much larger intracratonic depositional system that was progressively fragmented by major convergent tectonic events including the latest Neoproterozoic to earliest Paleozoic Petermann Orogeny, and the mid to late Paleozoic Alice Springs Orogeny.

Exploration history

Petroleum exploration in the Amadeus Basin has been almost entirely restricted to the better studied and more accessible Northern Territory portion. The first exploration well was drilled in 1963, with the large Mereenie oil- and gasfield and Palm Valley gasfield being discovered in 1964 and 1965, respectively. Both fields have been producing since the mid-1980s, via an oil pipeline to Alice Springs and gas pipelines to Alice Springs and Darwin.

Early exploration was focused on prominent surface anticlines, with later exploration focusing on seismically defined targets beneath cover. Other discoveries include the Dingo gasfield (discovered 1981), and significant shows have been encountered in other wells. The Dingo gasfield is now operated by Central Petroleum Pty Ltd and proposed to commence production in 2015, supplying gas via pipeline to the Alice Springs power station. When this happens it will be the first commercialisation of Precambrian reservoired hydrocarbons in Australia.

Petroleum prospectivity

Studies of the Northern Territory portion of the Amadeus Basin have identified at least four petroleum systems. The youngest, the Ordovician Larapintine petroleum system, is associated with the large, producing Palm Valley gasfield and the Mereenie oil- and gasfield, and is responsible for significant shows elsewhere across the northern half of the basin. However, this petroleum system is not considered to be prospective in the Western Australian Amadeus Basin because Ordovician strata are thin, only locally preserved, and the Horn Valley Siltstone source unit is not recognised west of the border.

The older petroleum systems are all related to Neoproterozoic sources. These systems are associated with one gasfield proposed to come on stream in 2015 (Dingo) and significant oil and gas shows in a number of wells, and are the target of ongoing exploration in the Northern Territory.

Find out more about the stratigraphy and petroleum prospectivity of the Amadeus Basin (page 26)