Sydney Basin
Last updated:7 June 2023
Basin Details and Geological Overview
The Permo-Triassic Sydney Basin straddles Australia's central eastern coast in New South Wales. The basin covers 64 000km2, 36 000km2 onshore and 28 000km2 offshore under water depths of up to 4 500 metres. The Sydney Basin is part of a major basin system that extends over 1 500km from the Bowen Basin in Queensland through to the Gunnedah Basin in NSW. Onshore, the basin contains 4 500 metres of Permo-Triassic clastic sediments, while the offshore basin contains 6 000 metres of sediments. The basin overlies the Lachlan Fold Belt and Late Carboniferous volcanoclastic sediments. The basin formed during extension in the Early Permian, with half-graben infilled with the Dalwood and Talaterang Groups. Foreland loading followed with the compression of the Currarong Orogen in the Early Permian. Late Permian uplift associated with the New England foreland loading phase resulted in the formation of depocentres with the northeast Sydney Basin. These depocentres filled with pyroclastic and alluvial-paludal sediments of the Newcastle Coal Measures. In the Triassic, uplift of the offshore basin resulted in reworking of Permian sediments in fluvial environments. The basin underwent a final phase of deformation (thrusting) in the Middle Triassic. Extension and breakup in the Tasman Sea beginning in the Late Cretaceous resulted in the current structural boundaries of the basin's eastern margin.
Over 100 wells have been drilled in the onshore Sydney Basin, although no wells have yet been drilled offshore. The onshore basin contains rich coal deposits with associated natural gas and minor oil shows. The geochemistry of oil shows indicate a terrestrial source from a clay-rich environment, although not associated with the coal facies. The main trap types are anticlinal and overthrust, with some structural reactivation during Tasman Sea rifting.
- ProvExplorer - Sydney Basin Details and Geological Overview
Basin Summary Table
| State(s) | New South Wales | |
| Area (km2) | Offshore | 28 000 |
| Onshore | 36 000 | |
| Maximum thickness (m) | > 6 000 | |
| Age Range | Permian-Triassic (Jurassic and Cretaceous section believed to have existed but now eroded). | |
| Basin | Overlies | Palaeozoic granites, volcanics and metasediments. |
| Underlies | - | |
| Subdivisions | Informal 'West', 'Central', 'South' and 'North' subdivisions are used onshore. | |
| Other | Offshore structure quite different from onshore. | |
| Indicators | Knowledge | Detailed field scale geophysical and well data onshore; regional geophysical data only offshore. |
| Basin type | Convergent margin foreland thrust loaded basin. | |
| System(s) | Gondwanan. | |
| Water Depth (m) | 0-4 000 | |
| Exploration | Status | Frontier (offshore). |
| Wells | 0 offshore, 115 onshore petroleum exploration wells. | |
| Seismic line-km | Sparse 2D regional coverage offshore. | |
| Discoveries | Nil | |
| Shows | Widespread oil and gas shows have been encountered throughout the section. | |
| HC evidence | Active petroleum system (Maung and others, 1993). | |
| Geology | Source(s) | Late Permian coal measures and marine shales. |
| Reservoirs | Permian shallow marine to fluvial sands (but often affected by diagenesis); Triassic Narabeen Group has excellent reservoirs. | |
| Seals | Numerous Permo-Triassic intra-formational seals. | |
| Trap types | 1) Wrench related structures, 2) overthrust traps, 3) mild basin inversion features, 4) extension down to basement fault bound blocks, 5) sub-thrust traps, 6) stratigraphic traps, 7) extensional, combination traps. | |
| Palaeogeographic summary | Early Permian: dominantly marine; late Early Permian to Late Permian: dominantly fluvial, with coal measures; Triassic: dominantly fluvial but some marine and volcanics; Jurassic-Cretaceous: eroded. | |
| Timing | Oil generation | Commenced Middle Jurassic to Early Cretaceous for Late Permian sources depending on location and amount of eroded section, late generation still occurring. A Late Cretaceous peak is probable. |
| Gas generation | Early Cretaceous to present. | |
| Trap formation | Types 2, 4 and 5 Early Permian, type 1 Early Permian to Triassic, type 3 Late Permian, type 6 Late Permian to Triassic, type 7 Early Cretaceous. | |
| Other key times | Major Late Cretaceous erosion accompanied breakup between Australia and the Lord Howe Rise. | |
| Other important information | 1) The offshore basin lies under a while migration path for several months of the year; 2) The onshore basin includes large urban areas. | |
| Geoscience Australia products available | 1) Harrington and others, 1989; 2) Maung and others, 1997. 3) Cadman and others, 1998. | |
Key References
| Author(s) | Year | Title |
|---|---|---|
| Alder, J.D., Hawley, S., Maung, T., Scott, J., Shaw, R.D., Sinelinikov, A. and Kouzmina, G. | 1998 | Prospectivity of the offshore Sydney Basin: A new prospective. The Australian Petroleum Production and Exploration Association (APPEA) Journal, 38(1), 68-91 |
| Bembrick, C.S., Herbert, C., Scheibner, E. and Stuntz, J. | 1973 | Structural subdivisions of the New South Wales portion of the Sydney-Bowen Basin. Geological Survey of New South Wales, 116, 105-117 |
| Bowman, H.N. | 1981 | Brief notes on the offshore coal potential of New South Wales. Geological Survey of New South Wales, Report GS 1981/372 |
| Bradley, G.M., Yoo, E.K., Moloney, J., Beckett, J. and Richardson, S.J. | 1985 | Petroleum data package, Sydney Basin NSW. NSW Geological Survey Report GS 1985/004, 229 |
| Brakel, A.T. | 1986 | Global sea level change as a method of correlating the Late Permian coal measures in the Sydney, Gunnedah and Bowen Basins, eastern Australia. BMR Journal of Australian Geology and Geophysics, 10, 79-116 |
| Branagan, D., Herbert, C. and Langford-Smith, T. | 1976 | An outline of the geology and geomorphology of the Sydney Basin, Science Press, Department of Geology and Geophysics, University of Sydney |
| Cadman, S. J., Pain, L. and Vuckovic, V. | 1998 | Bowen and Surat Basins, Clarence Morton Basin, Sydney Basin, Gunnedah Basin and other minor onshore basins, Queensland, NSW and NT. Australian Petroleum Accumulations Report 11, Bureau of Resource Sciences, Canberra |
| Carey, S.W. | 1969 | Tectonic framework of the Sydney Basin. Abstracts for the 1st, 2nd, 3rd and 4th Symposia on Advances in the Study of the Sydney Basin. University of Newcastle, NSW, 53-59 |
| Doyle, H.A., Underwood, R. and Polack, E.J. | 1966 | Seismic velocities from explosions off the central coast of New South Wales. Journal of the Geological Society of Australia, 13, 355-372 |
| Eadington, P.J., Hamilton, P.J. and Bai, G.P. | 1991 | Fluid History Analysis - A New Concept for Prospect Evaluation. APEA Journal/Sydney Basin, 282-294 |
| Evans P.R. and Migliucci, A. | 1991 | Evolution of the Sydney Basin during the Permian as a foreland basin to the Currarong and New England Orogen. Newcastle Symposium on the Advances in the Study of the Sydney Basin, University of Newcastle, Department of Geology, v.25, 22-29 |
| Finlayson, D.M. and McCracken, H.M. | 1981 | Crustal structure under the Sydney Basin and Lachlan Fold Belt, determined from explosion seismic studies. Journal of the Geological Society of Australia, 28, 177-190 |
| Gostin, V.A. and Herbert, C. | 1973 | Stratigraphy of the Upper Carboniferous and Lower Permian sequence, southern Sydney Basin. Journal of the Geological Society of Australia, 20, 49-70 |
| Grybowski, D.A. | 1992 | Exploration in Permit NSW/P10 in the offshore Sydney Basin. APPEA Journal, 32, 251-263 |
| Harrington, H.J. | 1982 | Keynote Address: Tectonics and the Sydney Basin. Abstracts for the 16th Symposium on Advances in the Study of the Sydney Basin, 15-19. University of Newcastle, NSW |
| Harrington, H.J., Brakel, A.T. and Hunt, J. | 1983 | Tectonic settings of central and eastern Australian Permian coal basins. 6th Australian Geological Convention, Geological Society of Australia, Abstracts 9, 278 |
| Harrington. H.J., Brakel, A.T., Hunt, J.W., Wells, A.T., Middleton, M.F., O'Brien, P.E., Hamilton, D.S., Beckett, J., Weber, C.R., Radke, S., Totterdell, J.M., Swaine, D.J. and Schmidt, P.W. | 1989 | Permian coals of Eastern Australia. Bureau of Mineral Resources, Australia, Bulletin 231 |
| Hawley, S.P., Glen, R.A. and Baker, C.Y. | 1995 | 1:100,000 scale Newcastle Coal Field Regional Geology Map. NSW Department of Mineral Resources, Geological Survey of NSW |
| Herbert, C. | 1987 | Petroleum Prospectivity in the Sydney Basin. Newcastle Symposium on the Advances in the Study of the Sydney Basin, University of Newcastle, Department of Geology, v.21, 107-113 |
| Maung, T.U., Alder, D., Shaw, R. and Hawley, S. | 1997 | Offshore Sydney Basin petroleum prospectivity bulletin. Petroleum Resources Branch, Bureau of Resource Sciences |
| Mayne, S.J., Nicholas, E., Bigg-Wither, A.L., Rasidi, J.S. and Raine, M.J. | 1974 | Geology of the Sydney Basin - A Review. Australian Bureau of Mineral Resources, v.149, 229 |
| Middleton, M.F. | 1989 | Coal-Rank Trends of Eastern Australia in Permian Coal Basins. IN: Harrington, H.J. (Editor) 'Permian Coals of Eastern Australia', Bureau of Mineral Resources Bulletin 231, 333-352 |
| Packham, G.H. (editor) | 1969 | The Geology of New South Wales. Geological Society of New South Wales Incorporated. Journal. Geological Society of Australia, 16(1). 654 |
| Robertson Research (Aust.) Pty Ltd. | 1981 | Exploration Report, PEL 242,243,244. NSW Department of Mineral Resources Report PGR 1982/02 |
| Shepherd, J. and Huntington, J.F. | 1981 | Geological fracture mapping in coalfields and the stress fields of the Sydney Basin. Journal of the Geological Society of Australia, 28, 299-309 |
| Smyth, M. | 1983 | Hydrocarbon Source Rock in the Sydney and Gunnedah Basins. Advances in the Study of the Sydney Basin. Proceedings of the 17th Symposium, University of Newcastle |
| Tye, S.C, Fielding, C.R. and Jones, B.J. | 1996 | Stratigraphy and Sedimentology of the Permian Talaterang and Shoalhaven Groups in the southernmost Sydney Basin, NSW. Australian Journal of Earth Sciences (1996), v.43, 57-69 |