Understanding potential resource prospectivity: 1-D burial and thermal history modelling of the Adavale Basin

Lateral variation in maturity of potential Devonian source rocks in the Adavale Basin have been investigated using nine 1D burial thermal and petroleum generation history models, constructed using existing open file data. These models provide an estimate of the hydrocarbon generation potential of the basin. Total organic carbon (TOC) content and pyrolysis data indicate that the Log Creek Formation, Bury Limestone and shale units of the Buckabie Formation have the most potential as source rocks. The Log Creek Formation and the Bury Limestone are the most likely targets for unconventional gas exploration. The models were constructed using geological information from well completion reports to assign formation tops and stratigraphic ages to then forward-model the evolution of geophysical parameters. The rock parameters, including facies, temperature, organic geochemistry/petrology, were used to investigate source rock quality, maturity and kerogen type. Suitable boundary conditions were assigned for paleo-heat flow, paleo-surface temperature and paleo-water depth. The resulting models were calibrated using bottom hole temperature and measured vitrinite reflectance data. The results correspond relatively well with published heat flow predictions, however a few wells show possible localised heat effects that differ from the overall basin average. The models indicate full maturation of the Devonian source rocks with generation occurring during the Carboniferous and again during the Late Cretaceous. Any potential accumulations may be trapped in Devonian sandstone, limestone and mudstone units, as well as overlying younger sediments of the Mesozoic Eromanga Basin. Accumulations could be trapped by localised deposits of the Cooladdi Dolomite and other marine, terrestrial clastic and evaporite units around the basin. Migration of the expelled hydrocarbons may be restricted by overlying regional seals, such as the Wallumbilla Formation of the Eromanga Basin. Unconventional hydrocarbons are a likely target for the Adavale Basin with potential either for tight or shale gas in favourable areas from the Log Creek Formation and Bury Limestone.