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AAPG Bulletin

Abstract

AAPG Bulletin, V. 102, No. 3 (March 2018), P. 483-507.

Copyright ©2018. The American Association of Petroleum Geologists. All rights reserved.

DOI: 10.1306/0608171609417067

Burial and exhumation history of the Galilee Basin, Australia: Implications for unconventional hydrocarbon prospectivity

Amy I’Anson,1 Ian Deighton,2 R. Dietmar Müller,3 Adriana Dutkiewicz,4 and Christian Heine5

1Earthbyte Group, School of Geosciences, The University of Sydney, Camperdown, New South Wales 2006, Australia; [email protected]
2Geological Products and Services–Interpretation, TGS, 1 The Crescent, Surbiton, Surrey KT6 4BN, United Kingdom; [email protected]
3Earthbyte Group, School of Geosciences, The University of Sydney, Camperdown, New South Wales 2006, Australia; [email protected]
4Earthbyte Group, School of Geosciences, The University of Sydney, Camperdown, New South Wales 2006, Australia; [email protected]
5Earthbyte Group, School of Geosciences, The University of Sydney, Camperdown, New South Wales 2006, Australia; present address: Specialist Geosciences, Shell Global Solutions International B.V., 2288 GS Rijswijk, The Netherlands; [email protected]

ABSTRACT

This multidisciplinary study describes the burial and exhumation history of the frontier Galilee Basin in central Queensland, Australia, with implications for understanding its geohistory and unconventional gas prospectivity. Seismic interpretation, stratigraphic mapping, and an analysis of exhumation through quantifying overcompaction show total subsidence of approximately 2 km (∼6600 ft) from the Carboniferous to the Late Cretaceous, punctuated by two major exhumation events. Triassic exhumation was less than 600 m (<1970 ft), whereas Late Cretaceous exhumation was in the order of 1000 m (3300 ft), increasing eastward to greater than 1600 m (5250 ft). Geohistory reconstructions show that Permian coal measures generated up to 45 m3/t (1590 ft3/t) of gas when modeled temperatures exceeded 100°C (210°F) during maximum burial of 1.5–2 km (4920–6560 ft) in the Late Cretaceous. In the Carboniferous to the mid-Cretaceous, the basin was situated to the west of the Eastern Australian subduction zone, where proto-Pacific oceanic lithosphere was subducted until circa 100 Ma, when subduction ceased. Our study shows that the geohistory of the basin is characterized by rapid subsidence of 50 m/m.y. (165 ft/m.y.) followed by rebound at circa 95 Ma resulting in an uplift and erosion phase. The undersaturation of the coals at present day is explained by this uplift event. Carbon isotopes indicate that the remaining gas (<8 m3/t [<280 ft3/t]) is of mixed biogenic and thermogenic origin. Therefore, dynamic surface topography driven by subduction dynamics and slab breakoff had a profound effect on the subsidence, uplift, and resource potential of the Galilee Basin.

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