Organic petrography and thermal maturity of the Permian Roseneath and Murteree shales in the Cooper Basin, Australia

The Permo-Triassic Cooper Basin is one of the largest intracratonic basins in Australia, covering approximately 130,000 km2 in South Australia and Queensland. The basin is one of Australia's major onshore hydrocarbon province and most prospective region for both conventional and unconventional hydrocarbon explorations. Organic petrography and thermal maturity of two Permian lacustrine shale units in the Cooper Basin, the Murteree and Roseneath shales, were investigated on 21 wells with the objective of evaluating the gas generating potential of these units. Vitrinite reflectance values for the Murteree and Roseneath shales range between 1.17% and 2.00%. Macerals show systematic changes in properties relative to maturity rank. A range of maceral compositions, dominated by vitrinite group macerals, are present in both units, which vary between rich and very rich in organic content. Rock-Eval data suggest fair to very good kerogen quality (of kerogen types II, III, and IV ranging from immature to mature) and imply a mostly gas-prone generation potential in the shales.