Northern Lawn Hill Platform - modelling the 'great-grandparent' emerging region

The northern Lawn Hill Platform (nLHP) of the Isa Superbasin, far northwest Queensland is currently considered an emerging region and is an area of renewed interest for unconventional gas. Petroleum systems analysis presented here will improve the understanding of burial history, source rock richness and maturity of the nLHP. A pseudo-3D geological model was built and calibrated, in combination with 1D burial and thermal history modelling for two key wells. These were combined with source rock characteristics which helped assess the hydrocarbon generation potential for two source rocks, allowing a broader assessment of petroleum prospectivity of the nLHP. The study focussed on two significant source rocks; the Lawn 4 Sequence and the River Supersequence. Maturity modelling of the Lawn 4 Sequence at Desert Creek 1 and Egilabria 1 predicted equivalent vitrinite reflectance (EqVR) of over 1.2% and 2%, respectively. The River Supersequence was modelled as overmature at both wells. Combining these results with the pseudo-3D model and source rock characteristics demonstrated that the highest maturities are encountered in the deepest depocentres to the east and gradually decrease in maturity to the west, indicating some potential for wet gas. Modelling results also show generation of varying amounts of gas and oil from each potential source rock. Overall, due to the age of the sediments, maximum depth of burial and high paleotemperatures, the most likely hydrocarbon phase is gas from primary generation and supplemented by secondary gas from oil cracking. In spite of high maturities, the presence of gas shows from the Egilabria prospect support continued exploration interest in this region for unconventional hydrocarbons.