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Abstract
The Clarence‐Moreton Basin contains abundant oil‐prone organic matter of terrestrial origin particularly in the Walloon Coal Measures and, to a lesser extent, in the Koukandowie Formation. This oil‐prone character is reflected in the petrographic composition, pyrolysis yields, kerogen elemental composition and extractable hydrocarbon yields of shale and coal. Maturation levels vary from immature to marginally mature in the west to overmature in the eastern part of the basin in New South Wales. Calculations based on Rock Eval data show that significant oil generation occurred in a narrow maturation range (0.8–1.0% vitrinite reflectance) and that migration has been highly efficient. Maturation modelling and fission track analyses indicate that hydrocarbon generation occurred 80–100 Ma during a period of high heat flow when the Tasman Sea spreading ridge was adjacent to the southeastern side of the Logan Sub‐basin. Despite the abundance of oil‐prone source rocks, the basin is considered to be largely gas‐prone because the drainage areas for many prospects are overmature.