From Geoscience Australia
JSON format icon JSON RDF format icon RDF ISO19115-3 XML

Velocity Analysis and Depth Conversion in the Offshore Northern Perth Basin

Created 16/10/2025

Updated 16/10/2025

JSON format icon JSON RDF format icon RDF ISO19115-3 XML

The northern Perth Basin is an elongate sedimentary basin, located off the southwestern margin of Australia. The basin is prospective for petroleum resources, but is relatively under-explored, and the nature of the sediment-basement contact is relatively unknown due to a high degree of structuring and deep basement depth inhibiting seismic imagining. Accurate depth conversion of seismic interpretation is vital for use as constraints in gravity modelling and in other basin modelling tasks, but depth conversion requires good quality seismic velocity information. The number and distribution of wells with velocity information in the northern Perth Basin is poor, but there exists a large amount of seismic stacking velocities. Seismic stacking velocities are an outcome of seismic processing and are thus not a direct measurement of the speed of sound in rocks. To improve the quality of stacking velocities we propose a methodology to calibrate stacking velocities against well velocities, which is as follows:

Check each velocity dataset for errors Modify the datum of each dataset to the sea floor Convert all datasets to TWT and depth domain Resample all velocity datasets to the same depth intervals Cross plot stacking velocity depths near a well site with corresponding well depths Fit a linear polynomial to this cross-plot (higher order polynomials were tried also), and determine calibration coefficient from the gradient of the polynomial.
Grid calibration coefficients Multiply depths derived from stacking velocities by calibration coefficient grid

An assessment of depth conversion errors relative to wells shows that this methodology improves depth conversion results to within ±50m; this depth uncertainty translates into a gravity anomaly error of about ±20 gu, which is acceptable for regional scale gravity modelling.

Files and APIs

Tags

Additional Info

Field Value
Title Velocity Analysis and Depth Conversion in the Offshore Northern Perth Basin
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/c9c0f2ca-6b90-4b7e-a2d2-cc37ba9b65e3
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 20/04/2018
Geospatial Coverage
Map data © OpenStreetMap contributors
{
  "coordinates": [
    [
      [
        108.0,
        -31.0
      ],
      [
        116.0,
        -31.0
      ],
      [
        116.0,
        -23.0
      ],
      [
        108.0,
        -23.0
      ],
      [
        108.0,
        -31.0
      ]
    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Velocity Analysis and Depth Conversion in the Offshore Northern Perth Basin". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/velocity-analysis-and-depth-conversion-in-the-offshore-northern-perth-basin1