Stepping off the edge: the geological framework of deepwater northern Australia
Ciaran Lavin A * , Angus Goody A and Ian Longley BA Woodside Energy Group Ltd, Perth, WA, Australia.
B GIS-Pax, Perth, WA, Australia.
The APPEA Journal 63 S257-S262 https://doi.org/10.1071/AJ22253
Accepted: 14 March 2023 Published: 11 May 2023
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of APPEA.
Abstract
The northern part of deepwater Western Australia and the adjacent Indonesian territory is a vast, underexplored region which includes an area of Triassic geology atypical of the region. Seismic data highlights a substantial elongate Triassic depocentre mappable from the northern margin of the Browse Basin northwards to the Timor Trough. This is informally named the Outer Ashmore Trough. The Outer Ashmore Trough is bounded by an inboard hinge-zone. The axis of the trough extending beneath the Ashmore Reef-1 and North Hibernia-1 wells. The western flank (only partially mappable) is a steeply dipping hinge-zone bounded by an outer high. The trough is mappable northwards, until it is incorporated into the imbricate wedge of the Timor Trough. The trough is floored by thickened Early Triassic shales of the Mount Goodwyn Formation (coeval to the Bedout petroleum system in the vicinity of the Dorado Field). This shale-prone marine interval is succeeded by a thick shallow marine clastic interval incorporated into seaward-dipping gravity-driven faults with an interpreted decollement in the Early Triassic shales. The Norian was dominated by a broad carbonate platform not observed elsewhere on the north-western Australian margin. This interval shares similarities with the outcropping Triassic in Timor Leste. A likely interpretation is that the Outer Ashmore Trough succeeds hyperextended Late Permian rifting. The trough and its adjacent margins offer prospectivity of a potentially significant scale.
Keywords: Ashmore Platform, Ashmore Reef, laccolith, North Hibernia, Permian, post-rift, Timor Leste, Timor Trough, Triassic.
Ciaran Lavin is a Geological Advisor at Woodside. Ciaran joined Woodside in 1998 after working for the Geological Survey of Victoria for 3 years, focussed on the Otway Basin. Whilst at Woodside, Ciaran has worked a variety of roles in basins across the world, including the Atlantic margin basins, the Mediterranean and Australia in exploration, new ventures and business development roles. Ciaran currently works in the New Basins Team in Woodside’s Exploration and Development Division seeking international opportunities. |
Angus Goody graduated from the Australian National University in 1991 with a BSc (Hons) in Geology and Geophysics. He joined BHP in 1992 as a Geophysicist and worked at BHP for 30 years on a variety of exploration, appraisal and development projects out of BHP’s Melbourne, London, Houston and Perth offices. Since the merger of BHP and Woodside in June 2022, he has worked in the Australia Exploration Team in Woodside’s Exploration and Development Division. |
Ian Longley is a Petroleum Geologist with 34 years of experience who has worked for LASMO, Woodside, Shell and Oil Search in various locations around the planet in junior and executive exploration roles. He has specialised in the plate tectonic evolution, regional petroleum geology, play and prospect analysis and the hunt for new exploration opportunities in the Australasian region. He runs two industry training courses on the Petroleum Geology of SE Asia (www.pgsea.com) and the NW Shelf (www.pgnws.com) and has published extensively on regional petroleum geology in both areas. He is also joint founder of the Player Exploration and Play Analysis software (www.gis-pax.com). |
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