Development of a 3D geological model of the Clarence-Moreton Basin: on the challenge of integrating petroleum systems and groundwater systems approaches

Abstract

One of the key challenges to assist in the understanding of the potential impacts of coal seam gas (CSG) extraction is the development of robust geological and numerical models. In the Clarence-Moreton Basin, this task is complicated by the need to integrate shallow alluvial aquifers (typically less than 30 m thick) and deep bedrock aquifers, which can have a combined thickness of up to approximately 3,500–4,000 m in some parts of the basin. While shallow aquifers are not typically considered in petroleum reservoir studies, they are of great significance in the Australian government’s Bioregional Assessment Program as they host a range of valuable water-dependent assets. To address this challenge, the authors have developed a series of 3D geological models and flow simulation grids of different scales and resolutions, that will form the assessment’s basis. An accurate understanding of the potential connectivity pathways between the five major alluvial aquifer systems and the underlying Triassic to Cretaceous age units will underpin the prediction of potential impacts of depressurisation associated with CSG extraction from the Walloon Coal Measures, which is the major target of CSG exploration in the Clarence-Moreton Basin. The authors have used SKUA/GoCAD (Paradigm®) 3D geological modelling software to develop 3D geological models from elevation (DEM), and stratigraphic, seismic and lithological data to facilitate the development of reliable conceptual and numerical models that describe these connectivity pathways and constitute a road-map to a risk assessment of the potential impacts on water-related assets from CSG production in the basin.