VGP Technical Report 20 - Regional 3D geological framework model, Gippsland Basin, Victoria
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Product description:About the Victorian Gas Program: The Victorian Gas Program (VGP) is a comprehensive science-led program, incorporating geoscientific and environmental research to assess the risks, benefits and impacts of potential onshore conventional gas exploration and production. The program is also investigating the potential for further discoveries of onshore conventional and offshore gas in the Otway and Gippsland geological basins and assessing the feasibility of additional onshore underground gas storage in depleted reservoirs around the Port Campbell area. The VGP includes an extensive, proactive and phased community and stakeholder engagement program, through which the results of the scientific studies are being communicated. Executive summary: A new regional 3D geological framework model of the onshore and nearshore Gippsland Basin has been built as part of the Victorian Gas Program (VGP) using existing seismic and well data held by the Geological Survey of Victoria (GSV). This study represents a new and comprehensive compilation, analysis and interpretation of the available geological and geophysical data from the onshore and nearshore Gippsland Basin, incorporating data and knowledge from previous studies and interpretations. As part of the VGP geoscience program, GSV is studying petroleum systems components (reservoir, seal and source), to assess the petroleum prospectivity of the Gippsland Basin and estimate the potential for further conventional gas discoveries, onshore and offshore within Victoria’s jurisdiction. Geological framework models are constructed using specialist software from existing data including seismic surveys and well data that were obtained via previous exploration for underground resources (e.g. oil and gas, groundwater or minerals). Rock layers are interpreted from the datasets and the data points are joined together to create surfaces in three dimensions. These 3D surfaces represent geological units. In this study, the geological units that were interpreted include the top of the pre- Cretaceous basement, top of the Strzelecki Group, top of the Emperor, Golden Beach and Halibut subgroups, top of the Latrobe Group, near top of the Lakes Entrance Formation, near top of the Gippsland Limestone and near top of the Jemmys Point Formation. The top of the Latrobe Group is where most oil and gas has been found to date in the Gippsland Basin, and the Lakes Entrance Formation is the regional seal for the hydrocarbon discoveries. Hydrocarbon accumulations have also been discovered in geological units within and below the Latrobe Group. Mapping of these formations reveals the depositional history and evolution of the geographical features of the Gippsland Basin, that is the palaeogeography. The mapping is required to inform petroleum systems modelling, prospectivity assessments and a resource estimate. PetroAus Pty Ltd was engaged by GSV to construct a regional 3D geological framework model of the onshore Gippsland Basin. The project used all available seismic and well data acquired from previous petroleum exploration and data from groundwater and coal boreholes. Data from gravity surveying and geological studies were also incorporated in the construction of the 3D model. A total of 2916 line-kilometres of onshore 2D seismic data acquired between 1961 and 2015 was available for interpretation. In addition, 9622 line-kilometres of offshore 2D seismic was available. This seismic data, together with 745 wells and boreholes, was loaded into an IHS Kingdom™ (v. 2017) project, which was used to carry out the seismic interpretation and structural mapping. Non-seismic datasets such as wells and boreholes were used for subsurface mapping in regions where the seismic data coverage was sparse or non-existent. The regional 3D geological framework model covers most of the onshore Gippsland Basin and extends approximately 35 kilometres offshore to ensure that the new interpretation could be tied to an existing offshore model of the basin. A 3D two-way time model was constructed from the interpretation at key stratigraphic levels. A 3D velocity model was also built, using a combination of well-derived velocity information and seismic stacking velocities. This velocity model was then used to convert the time surfaces to depth, and the resulting depth surfaces, along with the interpreted faults, were used to construct a 3D depth model. Regional surface (time structure) maps were produced from merged horizon interpretations including a previous offshore interpretation. The final depth model, which includes geological attributes relevant to the different stratigraphic layers, provides a reference for future analysis and is available in Attachment A1 Gippsland Basin regional 3D geological framework model data package, along with all other project deliverables. Bibliographic reference: Powell, W.D., Nourollah, M.H., Tait, A.M., Saitta, A.J., Kirk, R., Woollard, K. & Bubrzycki, M., 2020. Regional 3D geological framework model, Gippsland Basin, Victoria. Victorian Gas Program Technical Report 20. Geological Survey of Victoria. Download: The downloadable version of this report is supplied in PDF format (130 MB), Att A1 data Kingdom ZIP (6.9 GB), Att A1 data ZIP (6.2 GB) and accessible version (DOCX 136 MB).. WARNING - you will need an NBN connection to download these larger data packages | ||||||
