Structural restoration of the Rovuma basin to analyse the tectonic history and the implications for the petroleum systems

The frontier deepwater Otway and Sorell basins lie offshore of southwestern Victoria and western Tasmania at the eastern end of Australia’s Southern Rift System. The basins developed during rifting and continental separation between Australia and Antarctica from the Cretaceous to Cenozoic. The complex structural and depositional history of the basins reflects their location in the transition from an orthogonal–obliquely rifted continental margin (western–central Otway Basin) to a transform continental margin (southern Sorell Basin). Despite good 2D seismic data coverage, these basins remain relatively untested and their prospectivity poorly understood. The deepwater (> 500 m) section of the Otway Basin has been tested by two wells, of which Somerset–1 recorded minor gas shows. Three wells have been drilled in the Sorell Basin, where minor oil shows were recorded near the base of Cape Sorell–1. As part of the federal government-funded Offshore Energy Security Program, Geoscience Australia has acquired new aeromagnetic data and used open file seismic datasets to carry out an integrated regional study of the deepwater Otway and Sorell basins. Structural interpretation of the new aeromagnetic data and potential field modelling provide new insights into the basement architecture and tectonic history, and highlights the role of pre-existing structural fabric in controlling the evolution of the basins. Regional scale mapping of key sequence stratigraphic surfaces across the basins, integration of the regional structural analysis, and petroleum systems modelling have resulted in a clearer understanding of the tectonostratigraphic evolution and petroleum prospectivity of this complex basin system.

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ABSTRACT: Integration of Petroleum Geochemical Data and Tectonic History: The Key to Understanding Jurassic to Lower Cretaceous Petroleum Systems in Southern Alberta and Northern Montana

AAPG Bulletin ◽

10.1306/61eecd1a-173e-11d7-8645000102c1865d ◽

2001 ◽

Vol 85 ◽

Author(s):

Cynthia L. Riediger1, Patrick Steve

Keyword(s):

Lower Cretaceous ◽

Geochemical Data ◽

Petroleum Systems ◽

Tectonic History ◽

Southern Alberta

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GEOCHEMICAL CHARACTERISTICS OF AUSTRALIA'S SOUTHERN MARGIN PETROLEUM SYSTEMS

The APPEA Journal ◽

10.1071/aj98017 ◽

1999 ◽

Vol 39 (1) ◽

pp. 297 ◽

Cited By ~ 10

Author(s):

D.S. Edwards ◽

H.I.M. Struckmeyer ◽

M.T. Bradshaw ◽

J.E. Skinner

Keyword(s):

Upper Cretaceous ◽

Petroleum System ◽

Geochemical Characteristics ◽

Source Rocks ◽

Liquid Hydrocarbons ◽

Petroleum Systems ◽

Tectonic History ◽

Southern Margin ◽

History Of ◽

Oil Source

The hydrocarbons discovered to date on the southern margin of Australia have been assigned to the Austral Petroleum Supersystem based on the age of their source rocks and common tectonic history. Modelling of the source facies distribution within this supersystem using tectonic, climatic and geographic history of the southern margin basins, suggests the presence of a variety of source rocks deposited in saline playa lakes, fluvial, lacustrine, deltaic and anoxic marine environments.Testing of the palaeogeographic model using geochemical characteristics of liquid hydrocarbons confirms the three-fold subdivision (Al, A2 and A3) of the Austral Petroleum Supersystem.Bass Basin oils are assigned to the Austral 3, Eastern View Petroleum System. The presence of oleanane in the biomarker assemblages of these oils, together with their negatively sloping, heavy, isotopic profiles, indicate derivation from Upper Cretaceous-Tertiary fluvio–deltaic source facies.In the eastern Otway Basin, oils of the Austral 2, Eumeralla Petroleum System are sourced by Lower Cretaceous (Aptian–Albian) coaly facies. Oil shows reservoired in the Wigunda Formation at Greenly-1 in the Duntroon Basin are possibly sourced from the Borda Formation and are assigned to the Austral 2, Borda Petroleum System.In the western Otway, Duntroon and Bight basins, a lack of definitive oil-source rock correlations precludes the identification of individual Austral 1 petroleum systems.

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New exploration opportunities in the southern Vlaming Sub-basin

The APPEA Journal ◽

10.1071/aj07026 ◽

2008 ◽

Vol 48 (1) ◽

pp. 371 ◽

Cited By ~ 4

Author(s):

Chris Nicholson ◽

Irina Borissova ◽

Andrew Krassay ◽

Chris Boreham ◽

Eric Monteil ◽

...

Keyword(s):

Source Rock ◽

Continental Margin ◽

Energy Security ◽

Burial History ◽

Liquid Hydrocarbons ◽

Structural Restoration ◽

Petroleum Systems ◽

Seismic Sections

As part of the Australian Government’s Energy Security Initiative, a new tectono-stratigraphic and petroleum systems study has been carried out in the Vlaming Sub-basin on Australia’s southwest continental margin. The study has included: biostratigraphic revisions for key wells; seismic interpretations of new and reprocessed data; geochemical assessments of key source rock intervals and liquid hydrocarbons; structural restoration of key seismic sections; and, 3D burial history modelling. Results have significantly improved our understanding of the Vlaming Sub-basin’s evolution and provide a basis for future exploration. New exploration opportunities in the southern Vlaming Sub-basin are open to explorers through the Australian Government’s 2008 Acreage Release.

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