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Light Hydrocarbon Geochemistry of the Bonaparte Basin, Including the Sahul Syncline, Malita Graben and Southern Petrel Sub-basin : Rig Seismic Survey 100 : Project 121.22

During April and May 1991 the Bureau of Mineral Resources conducted a combined deep crustal seismic and Direct Hydrocarbon Detection (DHD) survey (Rig Seismic Survey 100; Figure la) in the Bonaparte Basin, which is located in the Timor Sea off northwestern Australia. This survey is one of three combined seismic and DHD surveys (Surveys 97, 99 and 100) which have been conducted in the Timor Sea (Figure lb).

Survey 100 collected approximately 2540 line-km of DHD, together with approximately 2100 line-km of deep crustal seismic, gravity, and magnetic data. The DHD data from this survey complements that obtained in the same general area during Survey 99 (Bickford et al., 1992).

Several bottom-water light hydrocarbon anomalies were detected during the survey, mostly in the Petrel Sub-basin. The strongest anomalies were detected over the Petrel gas/condensate accumulation, in the vicinity of the Petrel-1 wellhead. Weak but aerially extensive anomalies were associated with the Tern gas/condensate accumulation.

The Petrel anomalies differed in character from those found over Tern, in that they were strong, up to two orders of magnitude above background, and were confined to a small area. In contrast, the Tern anomalies were weak, generally less than two-fold above background, but extended over a large area. A cross-plot model of percent hydrocarbon wetness versus methane has been used as a tool to predict the potential 'source' (oil prone, gas/condensate or dry gas) of bottomwater anomalies. The data from the anomalies detected over the Petrel and Tern gas/condensate accumulations show wetness trends from background (less than 1%) to levels of about 3.4%, with increasing methane concentrations up to 272 ppm (over Petrel).

The crossplot model trends are consistent with the hydrocarbon compositions in these gas/condensate accumulations. Several other hydrocarbon anomalies were detected away from exploration wells. These anomalies were typically weak, and usually of gas or gas/condensate 'source' (according to the crossplot model). However, one strong anomaly, detected in the southern Petrel Subbasin, had a maximum percent hydrocarbon wetness value greater than 16%, and an oilprone 'source' according to the crossplot model.

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Additional Info

Field Value
Title Light Hydrocarbon Geochemistry of the Bonaparte Basin, Including the Sahul Syncline, Malita Graben and Southern Petrel Sub-basin : Rig Seismic Survey 100 : Project 121.22
Type Dataset
Language English
Licence Creative Commons Attribution 4.0 International
Data Status inactive
Update Frequency asNeeded
Landing Page http://data.gov.au/dataset/d42e4acb-e5f0-48f0-8c8f-081c1be94b59
Date Published 2017-03-31
Date Updated 2017-03-31
Contact Point
Geoscience Australia
sales@ga.gov.au
Jurisdiction Commonwealth of Australia
Data Portal Australian Oceans Data Network CSW Harvester
Publisher/Agency Geoscience Australia
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