First Published: GEO ExPro, December 2017
Abstract
Polarcus, in collaboration with Spectrum and DownUnder GeoSolutions, is acquiring a 7,200 km2 RightBAND™ multi-client 3D seismic survey over the Vulcan Sub-basin, offshore north-west Australia. Historically, sub-optimal acquisition and processing strategies of the legacy data across the basin have not been able to address the geological and geophysical challenges, limiting understanding of existing proven plays and the evaluation of future upside. The broadband survey is being acquired by the Polarcus Naila using an XArray™ configuration of 10 x 112.5m x 8.1 km with a triple source and continuous recording.
The Vulcan Sub-basin
The Vulcan Sub-basin is a north-east to south-west trending Mesozoic extensional depocenter located in the western Bonaparte Basin between the Ashmore Platform to the north-west and the Londonderry High to the south-east (Figure 1). It extends south-westwards to connect with the Heywood Graben in the Browse Basin, opening north-eastward to the Nancar and Timor Troughs. The sub-basin comprises a complex series of horsts, grabens and terraces which developed as an intra-continental graben in response to extension in the late Callovian.
Figure: West–east Pre-SDM in-line across the southern Vulcan Sub-basin from the Cygnus multi-client 3D dataset.
The Callovian Unconformity marks the base of the syn-rift sequence, which is of critical importance as it contains the source rocks that provide the majority of hydrocarbon charge to reservoirs above, below and also within the syn-rift sequence. Widespread marine conditions prevailed during the syn-rift phase with deposition of shales of the Lower and Upper Vulcan Formations. The Jabiru, Challis and other intra-basinal horsts were partially to fully emergent at this time, and sand-rich fan deltas were shed from the Londonderry High and exposed horsts into the adjacent depositional lows, the Montara Formation forming from footwall erosion of exposed horsts and rotated fault blocks at the base of the syn-rift sequence.
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