Abstract The Tuna field, located on the northern margin of the offshore Gippsland Basin, has a wide range of natural CO 2 accumulations and provides a natural analogue that can be used to assess reservoir sealing capacity. A holistic approach is assumed for this study, which incorporates analysis of the hydrodynamic system in conjunction with evolutionary history, CO 2 and mineralogical distribution, fault mechanical stability and sealing potential. Integration of these parameters for each reservoir unit within the field produces potentially conflicting results regarding the West Tuna fault. Hydrodynamic evaluation has shown that the fault has a complex fluid flow history with significant variation at different reservoir levels, pressures suggest it is currently leaking across certain horizons in the intra-Latrobe while fault seal analysis predicts good sealing properties at those depths. The CO 2 distribution varies with depth, with higher concentrations of CO 2 found in the deeper, overpressured reservoirs of the early Latrobe. This in conjunction with the basin history and mineral studies suggests that the CO 2 distribution may be controlled by the fault and fault reactivity. Geomechanical studies show that pressures in these deeper reservoirs are insufficient to generate shear failure, while the likelihood for extensional fracturing, and thus the possibility for it to act as a pathway for vertical fluid flow, is very high. This study shows that an integrated approach can lead to a better understanding of the current day reservoir and fault properties, even if not all components resulted in the same conclusions. Moreover, it reduces the risk of mis-interpreting fault-seal properties based on less parameters.