Abstract
Analysis of water chemistry and pressure data from the Queensland sector of the Cooper and Eromanga Basins indicates that two regional fluid flow systems are operating within these basins. In the Eromanga Basin (Jurassic-Cretaceous) a southwestward and descending open flow system is evident, driven by the topographically induced Great Artesian Basin hydrodynamic regime. In the underlying Cooper Basin (Upper Carboniferous-Triassic) a closed system is reflected by overpressuring and ascending flow out of each of the major Permian troughs. Where the two systems interact and equilibrate, mixing of formation waters from Permian and Jurassic reservoirs is apparent in water chemistry data and potentiometric surface minima can be identified in vertical pressure profiles.
The water chemistry and pressure data have been used to identify hydraulic baffles within the Permian and Jurassic sequences. These barriers are likely to provide effective lateral or vertical seals and, once identified, can be targeted in regional mapping projects to identify potential stratigraphic traps. In addition to the potential exploration applications, regional hydrodynamic databases are also valuable in petrophysical evaluations, by providing estimates of water resistivity in areas with poor well control, and for estimating field limits when the only available pressure data are from hydrocarbon columns within crestal wells.
