Authors / CoAuthors
Lech, M.E. | Jorgensen, D.C. | Southby, C. | Wang, L. | Nguyen, V.
Abstract
The Early Cretaceous Gage Sandstone and South Perth Shale are a prospective reservoir-seal pair in the Warnbro Group of offshore Vlaming Sub-basin, Western Australia. Gage Sandstone reservoir plays include post-breakup pinch-outs against the Valanginian Unconformity, and 4-way dip closures with the South Perth Shale forming the top seal. Deposited as a lowstand component of the deltaic South Perth Supersequence, the Gage Lowstand Fan (previously referred to as the Gage Sandstone) infilled palaeotopographic lows of the Valanginian breakup unconformity. Sequence stratigraphic analysis was used to characterise the reservoir-seal pair by integrating 2D seismic interpretation, well log analysis and new biostratigraphic data. Palaeogeographic mapping of the South Perth Supersequence reveal a series of regressions and transgressions that lead to the infilling of the central palaeodepression. The Gage reservoir is a sand-rich submarine fan system and ranges from canyon-confined inner fan deposits to middle fan deposits on a basin plain. Major sediment contributions were from north-south trending canyons adjacent to the Mandurah Terrace. More detailed seismic facies mapping and well log analysis of the Gage Lowstand Fan determined that the sand sheets in the distal middle fan and stacked channelized sands in the inner fan may provide an extensive reservoir of good to excellent quality. Seal quality varies greatly and may explain the lack of exploration success at some structural closures. A re-evaluation of the regional seal determined the extent of the pro-delta shale facies within the South Perth Supersequence that provides an effective seal for the underlying Gage reservoir. 3D geological modelling confirms that the Gage reservoir exhibits properties suitable for hydrocarbon entrapment and CO2 storage. Migration path analysis identified the presence of multiple structural and stratigraphic closures at the top of the Gage reservoir, with the most favourable located in the Rottnest Trough. Previous petroleum systems modelling concluded that the maturity of some source rocks in the sub-basin likely occurred after the deposition of the effective seal. Deep-seated faults, penetrating the syn-rift section, are in direct contact with the Gage reservoir and it could be actively receiving hydrocarbon charge.
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nonGeographicDataset
eCat Id
83089
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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Keywords
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- External PublicationScientific Journal Paper
- ( Theme )
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- marine
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- WA
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
Publication Date
2015-01-01T00:00:00
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unknown
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geoscientificInformation
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[-33.0, -31.0, 115.0, 115.5]
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