1D depth burial history and thermal maturity modelling of the Toolebuc Formation, Queensland

The Toolebuc Formation in the Eromanga and Carpentaria basins in western Queensland shares many characteristics with successful tight oil plays in the US. A study by the Geological Survey of Queensland has examined key parameters for this formation, including depth, thickness, lithology, mineralogy, maturity (both vitrinite reflectance and Tmax), total organic carbon and mud gas compositions and identified a possible play fairway in the central Eromanga Basin. Mudgas wetness ratios indicate that in areas modelled to be more mature, oil may be present in the Toolebuc Formation. These areas are typically in the central Eromanga Basin where the Toolebuc Formation is deepest, though oil responses have been calculated for wells that are shallower. This is contradicted by the apparent maturity of the formation based on vitrinite reflectance and Tmax measurements. Initial burial history modelling of the six petroleum wells indicates that DIO Hammond–1, SSL Clinton–1, DIO Tanbar North–1 and DIO Marengo–1 are in main oil window (0.7–1.0 %Ro) while DIO Denley–1 and DIO Ingella–1 are in the early oil window (0.55–0.7 %Ro). A single erosional event of 550 m of the Winton Formation has been assumed for this modelling. These wells are the deepest intersections of the Toolebuc Formation where it has been modelled to have higher maturity, and mudgas wetness ratios indicate oil may be present. Further refinement of these models and examination of additional wells is needed to better understand the potential for the Toolebuc Formation to have generated petroleum.