Exploring for the Future (EFTF) is an Australian Government program led by Geoscience Australia, in partnership with state and Northern Territory governments. The first phase of the EFTF program (2016-2020) aimed to drive industry investment in resource exploration in frontier regions of northern Australia by providing new precompetitive data and information about their energy, mineral and groundwater resource potential. One key discovery was the identification of a large sedimentary depocentre concealed beneath the Cambrian Georgina Basin. This depocentre, up to 8 km deep, was termed the ‘Carrara Sub-basin’ by Geoscience Australia. It is interpreted to contain thick sequences of Proterozoic rocks, broadly equivalent to rocks of the greater McArthur Basin (Northern Territory) and northern Lawn Hill Platform and Mount Isa Province (Queensland), known to be highly prospective for sediment-hosted base metals and unconventional hydrocarbons. In order to test geological interpretations in the Carrara Sub-basin, the South Nicholson National Drilling Initiative (NDI) Carrara 1 stratigraphic drill hole was completed in late 2020, as a collaboration between Geoscience Australia, the Northern Territory Geological Survey (NTGS) and the MinEx CRC managing of the drilling operation. NDI Carrara 1 is the first drill hole to intersect Proterozoic rocks of the Carrara Sub-basin. It reached a total depth of 1751 m, intersecting ca. 630 m of Cambrian Georgina Basin overlying ca. 1100 m of Proterozoic carbonates, black shales and minor siliciclastics.
Geoscience Australia has undertaken a range of investigations on the lithology, stratigraphy and geotechnical properties of NDI Carrara 1. These analyses include geochronology, isotopic studies, mineralogy, inorganic and organic geochemistry, petrophysics, geomechanics, thermal maturity, and petroleum systems investigations. To increase the understanding of the petroleum potential, molecular hydrogen and helium potential of sedimentary and basement rocks, Geoscience Australia commissioned a fluid inclusion stratigraphy (FIS) study on the downhole samples. Here, volatile components ostensibly trapped with fluid inclusions are released and analysed revealing the level of exposure of the well section to migrating fluids. Integration of thin section (TS) preparations reveal to extent of oil trapping within fluid inclusions while microthemometry (MT) gives an estimation of fluid inclusion trapping temperature.
For NDI Carrara 1, FIS analysis was performed on 86 cuttings between 18 m and 282 m base depth and 342 cores between 283.9 m and 1750.45 m base depth, together with 27 samples prepared for TS and 4 samples for MT. To support this study, lithostratigraphic tops were interpreted and compiled by Geoscience Australia. The results of the study are found in the accompanying documents.
