Coupled stratigraphic and fault seal modelling used to describe trap integrity in the frontier Bight Basin,Australia |
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| Institution: | 1. Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, 0316 Oslo, Norway;2. The Center for Earth Evolution and Dynamics, University of Oslo, P.O. Box 1028, Blindern, 0315 Oslo, Norway;3. TGS, Lensmannslia 4, 1386 Asker, Norway;4. Department of Petroleum Engineering, University of Stavanger, 4036 Stavanger, Norway;1. Basins Research Group (BRG), Imperial College, Prince Consort Road, London, SW7 2BP, UK;2. Shell, 40 Bank Street, 1 Canada Square, Canary Wharf, London E14 5AB, UK;1. Coal Reservoir Laboratory of National Engineering Research Center of CBM Development & Utilization, China University of Geosciences, Beijing 100083, China;2. CSIRO Energy Flagship, Private Bag 10, Clayton South, VIC 3169, Australia;3. PetroChina Huabei Oilfield Company, Renqiu 062550, China;1. Centre for Tectonics, Resources and Exploration (TRaX), Australian School of Petroleum, University of Adelaide, Adelaide, SA 5005, Australia;2. Department of Geology & Petroleum Geology, University of Aberdeen, Aberdeen AB24 3UE, UK;3. CSIRO Energy, Australian Resources Research Centre, 26 Dick Perry Avenue, Kensington, WA 6151, Australia |
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| Abstract: | Top seals and faults represent key risks to trap integrity and therefore preservation of hydrocarbons in the frontier Ceduna Sub-basin, offshore Southern Australia. Due to a paucity of well data in the basin, to provide constraint to the stratigraphic distribution of the prospective Cretaceous deltaic and marine sequences, stratigraphic forward modelling was utilised to create facies, grain size and Vshale volumes. These modelled Vshale volumes were subsequently used to investigate the structural control(s) on potential hydrocarbon leakage and migration within key stratigraphic sequences in the sub-basin.A set of coarse (20 km horizontal resolution), large scale (1100 × 600 km) stratigraphic forward models simulated the deposition of Late Jurassic to Tertiary stratigraphic sequences in the sub-basin with an initial 1 Ma interval. Smaller (80 × 60 km), finer scale (0.5 km horizontal resolution, 200 ka interval), models focussing on the Tiger and Hammerhead Supersequences over the Trim 3D seismic survey were used to investigate fault seal and top seal frameworks, using shale gouge ratio and silt and shale thicknesses from Vshale volume. Four stratigraphic forward models were produced to match a range of estimates of Vshale derived from the Gnarlyknots-1A well, the only well penetrating the central Ceduna Sub-basin. These stratigraphies were in turn integrated into a geological model interpreted from the Trim 3D seismic survey creating a geocellular model to test potential migration and trapping scenarios for potential hydrocarbons generated in the sub-basin.Fault and top seal models from the most likely scenario suggest (i) restricted potential for structural trapping near the base of the Tiger Supersequence, (ii) the possible presence of a regional migration pathway associated with sandy shoreface deposits at the transition between the Tiger and Hammerhead Supersequences, and (iii) the association of intraformational top seals and increasing fault seal potential in the deltaic sediments of the Hammerhead Supersequence feasibly resulting in a series of stacked structural traps. |
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| Keywords: | Great Australian Bight Ceduna Sub-basin Stratigraphic forward modelling Fault seal Trapping frameworks |
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