Salt Walls in the Officer Basin Signature in Aero Magnetic Data

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Potential Fields for Petroleum Exploration:

Salt Walls in the Officer Basin Signature in Aero Magnetic Data

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Location Map: Officer Basin & Yowalga Sub Basin

• Huge Underexplored Basin

• Large Area - Extends from Western Australia into South Australia

• Some historic 2D seismic Coverage

• 500m line spaced magnetic data (coarse)

• Sparse Gravity data

• Very remote – land access issues could make further land seismic surveys difficult

YowalgaSubBasin

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Location Map: Yowalga Sub Basin

• Intra-Basin Table Hill Volcanics provide magnetic signature when ruptured

• Extensive Salt Diapirs in the South – negative density contrast in gravity data

• Salt Diapirs, Domes and Walls can act as hydrocarbon traps

• Seismic Line T080-007 traverses the Browne Salt Wall

Seismic line T080-007

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Seismic Line T080-007

Subtle first vertical derivative (1VD) Magnetic signature from breached Table Hill Volcanics

Salt diapirs are generally well imaged in Seismic reflection Data

In this case the Browne Salt Wall can be seen in the magnetic data because it has breached a sub horizontal magnetic layer (Table Hill Volcanics)

Browne Salt Wall

Table Hill Volcanics

Salt wall?

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Officer Basin – Browne Salt Wall

Browne Salt Wall

• The subtle magnetic response from the breached Table Hill volcanics is much more apparent in the gridded 1VD magnetic data

• The Browne Salt Wall is visible for 85 Kilometers in the gridded data

• This could provide the means to target further seismic surveys (salt wall = possible hydrocarbon trap)

• High resolution magnetic surveys would improve definition of salt wall

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“blind” Salt wall (has not breached volcanics)

Table Hill Volcanics

Browne Salt Wall

Gravity Response – Forward Model Airborne Systems

May not be seen in magnetic data if volcanics not breached

Low Density salt dome should produce a strong negative anomaly in airborne gravity and gravity gradiometer surveys

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Conclusions:

• Magnetic data can reveal salt diapirs in basins where they breach or disturb magnetic units

• Gravity data may reveal “blind” salt diapirs not evident in the magnetic data (i.e. where they do not breach or disprupt the overlying magnetic units)

• Both Airborne gravity/gradiometry and magnetic surveys can provide the means to focus expensive seismic surveys in the right areas

• Further reading• Salt tectonics in the Officer Basin: implications for trap formation and

petroleum exploration. Anelia Simeonova and Robert Iasky. ASEG Extended Abstracts 2004(1) 1 - 4 • http://www.publish.csiro.au/paper/ASEG2004ab132

• Using potential field data to map salt distribution in the Western Officer Basin, Western Australia.• http://www.publish.csiro.au/?act=view_file&file_id=ASEG2015a

b072.pdf