Unconventional hydrocarbons: Australia's old rocks prove their worth

Australia’s search for petroleum began in the onshore basins where extensive areas of Paleozoic marine sequences, with some high-quality source rock intervals and spectacular outcrop, encouraged sporadic exploration for many decades. For these efforts, there were some rewards, including the discovery of the Mereenie oil field in Ordovician rocks, the Amadeus Basin in 1960s, and the Blina discovery in Devonian carbonates in the Canning Basin during the early 1980s. Since the late 1980s, however, the focus of exploration has shifted offshore where more and larger discoveries were made in the Mesozoic marginal basins, which today contain about 90% or more of Australia’s conventional oil and gas. Now, however, the focus has shifted back to the onshore, recognising the potential for shale and tight gas and oil in these older rocks. The onshore basin area under exploration license has nearly doubled from 2010–12; several major international companies have joined local explorers in testing the worth of Australia’s lower Paleozoic and Proterozoic petroleum systems, and new discoveries have been made in several basins. Geoscience Australia and its partners in the state and NT surveys are undertaking new assessments and studies across a number of these basins.