As part of the reconceptualisation and redevelopment of a regional groundwater model for the assessment of cumulative impacts in the Surat Basin, a new regional geological model (the Geomodel) was constructed. The Geomodel was developed dominantly through primary stratigraphic interpretation of wireline logging of petroleum and gas wells and water bores.
At the core of the Geomodel are lithostratigraphic packages correlated from consistent and recognisable wireline log characteristics. The model includes the major stratigraphic units, from the basement underlying the Bowen and Surat basins through to the surface Cenozoic sediments. There has been a progressive evolution of the understanding of the formation and geology of the Surat and Bowen basins. Past stratigraphic interpretations have been undertaken over a long period of time by many entities, using multiple and often outdated stratigraphic schemas. While there is still debate about the exact location and extent of various units, the interpretation for the Geomodel focused on providing consistent lithostratigraphic packages for modelling and used (Green et al. 1997) as its main guide, with some deviation to ensure regional consistency in the lithostratigraphic units.
Over 38,000 individual lithostratigraphic picks from wireline data from more than 4,800 P&G wells and water bores was correlated for 25 Surat Basin surfaces and six Bowen Basin surfaces.
In addition to providing a regionally consistent set of surfaces the method adopted is considered to be both objective and repeatable since it relies primarily on analyses of wireline log data. The final Geomodel and underlying stratigraphic picks have been used by OGIA to support a range of other activities including: i) maximising the value of groundwater level and quality data stored in the Queensland groundwater database, by attributing each bore to one or more stratigraphic database; and ii) independently assessing whether or not CSG production wells extend into other aquifers.