Petroleum systems of the Proterozoic in northwest Queensland and a description of various play types

Abstract

As part of Queensland Government’s Strategic Resources Exploration Program, in conjunction with the Australian Government’s Exploring for the Future program, a study to improve the subsurface knowledge of Proterozoic basins in northwest Queensland (NWQ) is underway. Proterozoic sedimentary basins are prevalent across central and western Australia. Several of these basins have proven petroleum systems, with the best discoveries to date being in the Greater McArthur Basin, Northern Territory. Recent exploration and appraisal in the Beetaloo Sub-basin of the Greater McArthur Basin has identified large volumes of gas resources contained within unconventional shale reservoirs. In NWQ, the Isa Superbasin and overlying South Nicholson Basin are related in both age and likely deposition to the Greater McArthur Basin. The thick, extensive shale units of the Isa Superbasin are excellent source rocks, while the Mullera Formation in the South Nicholson Basin also has potential but has not been investigated in detail. There are several potential reservoirs within the Proterozoic section and younger units of the overlying Georgina and Carpentaria basins, including clastic and carbonate types. Exploration in the Isa Superbasin identified an estimated 22.1 trillion cubic feet of prospective resources (Armour Energy 2015) in unconventional shale reservoirs of the Lawn Hill Formation and Riversleigh Siltstone. This paper will discuss the stratigraphy, depositional and structural history of these Proterozoic basins and characterise their source and reservoir units using existing and recently acquired geophysical, geochemical, petrographic and petrophysical datasets. From this, several plays or play concepts will be identified and described to help understand the region’s potential for both conventional and unconventional petroleum resources.