Otway Basin

About this study area

The Otway Basin is a Jurassic to Cretaceous rift basin formed along the southern continental margin of Australia, with the South Australian Otway Basin where this study is focused, covering ~60,000 square kilometres onshore and offshore. The basin formed as a result of multiple rift, sag, and inversion events, where half-graben bounding normal faults were reactivate during inversion. The Otway Basin is relatively underexplored, with ~200 petroleum wells drilled in South Australia, Victoria, and Tasmania, though no commercial oil discoveries to this point.

Regional Structural Permeability Maps

These maps present three potential permeability maps based on shallow, intermediate, or steeply dipping faults.

Shallow Dipping Faults

This permeability map uses the FAST geomechanical risking method to determine the permeability likelihood of faults assumed to have shallow dip angles.

Moderately Dipping Faults

This permeability map uses the FAST geomechanical risking method to determine the permeability likelihood of faults assumed to have moderate dip angles.

Steeply Dipping Faults

This permeability map uses the FAST geomechanical risking method to determine the permeability likelihood of faults assumed to have steep dip angles.

Further Data

In addition to FAST fault maps, we also present maps of FAST geomechanical risking of fractures identified in 3D seismic surveys, and wellbore image logs.

Seismic Survey Fracture Maps

Fractures and sub-seismic scale faults were identified using a variety of seismic processing methods on the Pretty Hill Formation top in the Balnaves/Haselgrove 3D seismic survey. These structures were then geomechanically risked to test their reactivation likelihood using FAST.

Wellbore Image Log Data

Resistivity image logs produce a pseudo-image of the wellbore wall, allowing for the identification of fractures, both resistive (closed), and conductive (open). These can then be plotted on a FAST reactivation likelihood plot.