Product catalogue
How deep is the basement beneath the Otway Basin? Insight from semi-automated magnetic depth estimates
Over 8,200 line kilometres of gravity and magnetic data, acquired during the 2020 Otway Basin Seismic Program (OBSP), were combined with public domain survey and satellite data to produce seamless maps of the NW-SE trending deep-water Otway Basin. These data provide valuable information on the geometry and spatial extent of igneous rocks in the deep-water basin. While the top of basement can effectively be imaged from seismic reflection datasets onshore in the Otway Basin, it remains problematic in parts of the deep-water offshore region due to variable seismic data quality. Modelling of the magnetic line data provides an estimate of the depth to the top of basement, an important interface for understanding hydrocarbon prospectivity because it plays a key role in characterising the tectonic evolution of the basin, and thus the thermal maturation history of hydrocarbons.
Magnetic modelling was performed using a profile-based curve matching technique producing a depth estimate to the top of the magnetic body that is assumed to be the top of the basement. However, this assumption is flawed where there are volcanic or igneous intra-sedimentary rocks in the basin, as is the case for the Otway Basin where the interpretation of seismic reflection data shows highly reflective events corresponding to igneous features. In most parts of the basin, the modelling results show two layers: a shallow layer (depths < 1000m) corresponding to near surface volcanics, and a deeper layer (depths > 1000m) attributed to the top of the magnetic basement. Magnetic basement shows some similarities with basement picked on seismic reflection data, though in some areas the magnetic basement is shallower. The results also show that the depth to basement is not well resolved in areas with abundant intra-sedimentary igneous rocks. Further investigation is needed in such areas.
Presented at the 2024 Australian Society of Exploration Geophysicists (ASEG) Discover Symposium
Simple
Identification info
- Date (Creation)
- 2024-06-26T22:00:00
- Date (Publication)
- 2024-10-23T21:43:55
- Citation identifier
- Geoscience Australia Persistent Identifier/https://pid.geoscience.gov.au/dataset/ga/149690
- Cited responsible party
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Role Organisation / Individual Name Details Publisher Commonwealth of Australia (Geoscience Australia)
Voice Author PoudjomDjomani, Y.
Internal Contact Author Gunning, M.
Internal Contact Author Bernardel, G.
Internal Contact Author Nguyen, D.
Internal Contact Editor Hope, J.
Internal Contact Editor Miller, R.
Internal Contact
- Name
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Australian Society of Exploration Geophysicists (ASEG) 2024 Discover Symposium 15-18 October 2024 Hobart, Tasmania
- Purpose
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Extended abstract presented at the Australian Society of Exploration Geophysicists DISCOVER Symposium in October 2024. Modelling of the magnetic line data provides an estimate of the depth to the top of basement, an important interface for understanding hydrocarbon prospectivity because it plays a key role in characterising the tectonic evolution of the basin, and so the thermal maturation history of hydrocarbons.
- Status
- Completed
- Point of contact
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Role Organisation / Individual Name Details Resource provider Minerals, Energy and Groundwater Division
External Contact Point of contact Commonwealth of Australia (Geoscience Australia)
Voice Point of contact PoudjomDjomani, Y.
Internal Contact
- Spatial representation type
- Topic category
-
- Geoscientific information
Extent
))
- Maintenance and update frequency
- Not planned
Resource format
- Title
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Product data repository: Various Formats
- Website
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Data Store directory containing the digital product files
Data Store directory containing one or more files, possibly in a variety of formats, accessible to Geoscience Australia staff only for internal purposes
- Project
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Geophysics
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- Project
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Magnetics
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- Project
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Otway Basin
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- Keywords
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Depth to basement
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- Keywords
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Magnetics
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- Keywords
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hydrocarbon prospectivity
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- theme.ANZRC Fields of Research.rdf
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Applied geophysics
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- Keywords
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Published_External
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Resource constraints
- Title
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Creative Commons Attribution 4.0 International Licence
- Alternate title
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CC-BY
- Edition
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4.0
- Access constraints
- License
- Use constraints
- License
- Other constraints
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(c) Commonwealth of Australia (Geoscience Australia) 2024
Resource constraints
- Title
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Australian Government Security Classification System
- Edition date
- 2018-11-01T00:00:00
- Classification
- Unclassified
- Classification system
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Australian Government Security Classification System
- Language
- English
- Character encoding
- UTF8
Distribution Information
- Distributor contact
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Role Organisation / Individual Name Details Distributor Commonwealth of Australia (Geoscience Australia)
Voice facsimile
- OnLine resource
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Link to Conference Page
Link to Conference Page
- Distribution format
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- OnLine resource
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Link to Abstract
Link to Abstract
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Resource lineage
- Statement
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<div>The depth to magnetic source estimates and the top of basement were calculated using an adaptation of Naudy’s profile-based curve matching technique (Shi, 1991; Shi and Boyd, 1993). The technique was implemented in Tensor Research’s ModelVision V17 software and allows a great degree of input from the interpreter, and more control on the depth to magnetic source calculations. The result is a combination of simple bodies with depth to top and a match between measured and model data along each profile. All modelling work was done using a datum and projection of GDA94 and MGA54, respectively.</div><div><br></div><div>For most of modelling work, preference was given to lines perpendicular to the strike of the magnetic anomalies. Thus, the three main NW-SE tie lines from the OBSP survey were selected for modelling purposes. Due to software limitations, each full line could not be uploaded at once as they contained too many data points. The lines were truncated in several sections and modelled separately. The advantage of truncating the data was the ability to focus the modelling on targeted anomalies. In addition to the NW-SE lines, a few lines oriented NE-SW were selected where their orientation was perpendicular to the strike of the anomaly.</div><div><br></div><div>A total of 33 line sections were modelled, and 222 depths were estimated. Of these depths, only 131 were considered to be generated by basement while the remainder were attributed to shallow igneous rocks in the basin</div><div><br></div><div>The magnetic line data acquired during the 2020 Otway Basin Seismic Program were used to estimate the depth to the top of basement. The modelling results show that the basement is deeper in the central part of the basin (up to 10,000 m) and shallower along the inboard part of the basin (~2,000m). Comparison with basement picks from seismic interpretation show that the depth to magnetic basement is influenced by the abundance of intra-sedimentary igneous rocks in the basin, resulting in shallower depth estimates. One important result of this modelling is that most of the magnetic lines show a 2-layer model with shallow depths representing the location of intra-sedimentary volcanics and deeper sources correlating with basement depths. Further investigation is needed to integrate seismic horizons and pre-existing high resolution gravity data to increase the confidence of the modelling result. </div>
Metadata constraints
- Title
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Australian Government Security Classification System
- Edition date
- 2018-11-01T00:00:00
- Classification
- Unclassified
Metadata
- Metadata identifier
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urn:uuid/d18086a5-b893-4676-9adb-90e73e13aa72
- Title
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GeoNetwork UUID
- Language
- English
- Character encoding
- UTF8
- Contact
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Role Organisation / Individual Name Details Point of contact Commonwealth of Australia (Geoscience Australia)
Voice Point of contact PoudjomDjomani, Y.
Internal Contact
Type of resource
- Resource scope
- Document
- Name
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Conference Abstract
Alternative metadata reference
- Title
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Geoscience Australia - short identifier for metadata record with
uuid
- Citation identifier
- eCatId/149690
- Date info (Creation)
- 2024-10-22T05:31:49
- Date info (Revision)
- 2024-10-22T05:31:49
Metadata standard
- Title
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AU/NZS ISO 19115-1:2014
Metadata standard
- Title
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ISO 19115-1:2014
Metadata standard
- Title
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ISO 19115-3
- Title
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Geoscience Australia Community Metadata Profile of ISO 19115-1:2014
- Edition
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Version 2.0, September 2018
- Citation identifier
- http://pid.geoscience.gov.au/dataset/ga/122551