Six gas samples were collected from the possum belly (PB) of the shaker assembly during the drilling of NDI Carrara 1. The sample depths ranged from 1187 m to 1360 m and were from organic-rich Proterozoic rock units. The molecular composition and carbon and hydrogen isotope compositions of the individual PB gas components (methane, ethane, propane and carbon dioxide) suggest that the gases were sourced from local, thermally mature, organic-rich shales and siltstones. After taking into account the air and excess nitrogen content in the PB gases, the helium content of the PB gases is low while the molecular hydrogen contents is up to over a 100 times higher than the helium content. Both molecular hydrogen and helium likely have a major radiogenic origin. Based on the results, there is potential for a yet-to-be quantified unconventional hydrocarbon resource in the vicinity of the NDI Carrara 1 well.