Understanding of petroleum systems in the Bowen and Surat basins, where Australia’s first commercial oil field was discovered, can be advanced through a regional 3D petroleum systems model. The model allows testing of various scenarios with consideration given to key controls of the petroleum systems such as source rock quality, thermal maturity, presence of carrier beds and effectiveness of seals. Geochemical data, along with migration modelling suggest that petroleum present in Jurassic reservoirs are mostly derived from Permian source rocks of the underlying Bowen Basin that are fully mature for oil generation. The Jurassic source rocks, in general, are immature to marginally mature for oil generation and have largely generated biogenic methane. However, vitrinite reflectance and fluorescence analyses of organic matter indicate that, at basement highs where the basal heat flow is elevated, the lower Jurassic coals enriched with liptinite are early mature for oil generation and likely expelled minor amounts of oil into the Walloon Coal Measures. Thermal maturity modelling also suggests that basement highs such as Comet Ridge experienced greater post-maturation uplift compared with adjacent depocentres; in these areas, coal seam gas reservoirs demonstrate enhanced fracture permeability. In deeper parts of the Taroom Trough, several low-permeability Permian reservoirs are notably over-pressured due to retention of pore fluids and volume expansion resulting from secondary cracking of oil to gas. Such overpressure is a significant factor influencing unconventional petroleum exploration, and the petroleum systems model has simulated various scenarios of over-pressuring to predict potential regions of over-pressure across the Taroom Trough.
Mohinudeen Faiz (2026) studied this question.