No abstract available

Legacy product - no abstract available

Legacy product - no abstract available

The Bureau of Mineral Resources (BMR) collected 1430 line-km of bottom-water Direct Hydrocarbon Detection (DHD) data during a survey aboard R.V. Rig Seismic in the Durroon Sub-basin, the Otway Basin, the Torquay Sub-basin, and the Gippsland Basin, during late September and early October of 1991. No significant bottom-water anomalies were detected in the Durroon Sub-basin. Anomalous concentrations of light C2+ hydrocarbons were detected in the eastern Otway Basin. The anomalies were not extensive, comprising only a few data points representing a few kilometres in extent. One anomaly (of methane, ethane and propane) was accompanied by high levels of the biogenic hydrocarbons, ethylene and propylene, suggesting in-situ biogenic activity in the water column. However, anomalous concentrations of C7 and C8 hydrocarbons were also found here and at three other locations, and are from an unknown 'source'. A weak bottom-water anomaly was detected in the Torquay Sub-basin in the same location as an anomaly detected during an earlier survey (Rig Seismic Survey 89), two years previously. The weakness of the anomaly prevents a confident interpretation of the potential 'source' of the hydrocarbon anomaly, but the data suggests it is derived from a gas/condensate, or dry thermogenic gas 'source'. Several strong bottom-water anomalies were detected in the Gippsland Basin. Bottomwater anomalies were found near the Sunfish and Tuna oil/gas accumulations, in similar locations to anomalies found on Rig Seismic Survey 89, two years earlier. However, another previously-detected anomaly (near Barracouta) was not reproduced. Additional anomalies were found near Flathead, and to the west of Wahoo. The anomaly west of Wahoo was weak and in a similar area to that detected on Survey 89. The composition of most bottom-water hydrocarbon anomalies in the Gippsland Basin are indicative of a liquid-prone hydrocarbon 'source', while one anomaly in the northern sector of the survey area is indicative of a gas/condensate 'source'.

This report is part of a set delivered by Geoscience Australia on interpretation of data acquired during the summer of 2006/07 on seismic reflection, refraction and potential field survey GA-302. A 3D approach to the gravity modelling was necessitated by the irregular geological structure of depocentres and basement highs. Over 6000 m of sediment is interpreted in the deepest pockets. The tools developed to realise the 3D gravity modelling are described in some detail. The gravity modelling process is also presented with a view to easing the integration of 3D mapping methods with a traditional reflection seismic interpretation workflow in the marine sedimentary basin environment.

In September and October of 2011 Geoscience Australia surveyed part of the offshore northern Perth Basin in order to map potential sites of natural hydrocarbon seepage. The primary objectives of the survey were to map the spatial distribution of seepage sites and characterise the nature of the seepage at these sites (gas vs oil, macroseepage vs microseepage; palaeo vs modern day seepage) on the basis of: acoustic signatures in the water column, shallow subsurface and on the seabed; geochemical signatures in rock and sediment samples and the water column; and biological signatures on the seabed. Areas of potential natural hydrocarbon seepage that were surveyed included proven (drilled) oil and gas accumulations, a breached structure, undrilled hydrocarbon prospects, and areas with potential signatures of fluid seepage identified in seismic, satellite remote sensing and multibeam bathymetry data. Within each of these areas the survey acquired: water column measurements with the CTD; acoustic data with single- and multi-beam echosounders, sidescan sonar and sub-bottom profiler (sidescan not acquired in Area F as it was too deep in places); and sediment and biological samples with the Smith-McIntyre Grab. In addition, data were collected with a remotely operated vehicle (ROV), integrated hydrocarbon sensor array, and CO2 sensor in selected areas. Sampling with the gravity corer had limited success in many of the more shallow areas (A-E) due to the coarse sandy nature of the seabed sediments. This dataset comprises organic carbon and nitrogen concentrations and isotopes of seabed sediments.

In September and October of 2011 Geoscience Australia surveyed part of the offshore northern Perth Basin in order to map potential sites of natural hydrocarbon seepage. The primary objectives of the survey were to map the spatial distribution of seepage sites and characterise the nature of the seepage at these sites (gas vs oil, macroseepage vs microseepage; palaeo vs modern day seepage) on the basis of: acoustic signatures in the water column, shallow subsurface and on the seabed; geochemical signatures in rock and sediment samples and the water column; and biological signatures on the seabed. Areas of potential natural hydrocarbon seepage that were surveyed included proven (drilled) oil and gas accumulations, a breached structure, undrilled hydrocarbon prospects, and areas with potential signatures of fluid seepage identified in seismic, satellite remote sensing and multibeam bathymetry data. Within each of these areas the survey acquired: water column measurements with the CTD; acoustic data with single- and multi-beam echosounders, sidescan sonar and sub-bottom profiler (sidescan not acquired in Area F as it was too deep in places); and sediment and biological samples with the Smith-McIntyre Grab. In addition, data were collected with a remotely operated vehicle (ROV), integrated hydrocarbon sensor array, and CO2 sensor in selected areas. Sampling with the gravity corer had limited success in many of the more shallow areas (A-E) due to the coarse sandy nature of the seabed sediments. This data set comprises carbonate and specific surface area measurements in the upper 2cm of seabed sediments.

Geoscience Australia has recently completed a marine survey in the offshore northern Perth Basin, off Western Australia (Jones et al., 2011b; Jones, 2011c, Upton and Jones, 2011). One of the principal aims of the survey was the collection of evidence for natural hydrocarbon seepage. The survey formed part of a regional reassessment of the basin's petroleum prospectivity in support of frontier exploration acreage Release Area W11-18. This reassessment was initiated under the Australian Government's Offshore Energy Security Program and formed part of Geoscience Australia's continuing efforts to identify a new offshore petroleum province. The offshore northern Perth Basin was identified as a basin with new frontier opportunities. New data demonstrated that proven onshore-nearshore petroleum system is also effective and widespread in the offshore (Jones et al., 2011a). Evidence for a Jurassic petroleum system was also demonstrated in the Release Area W11-18 (Jones et al., 2011a). The marine survey results provide additional support for the presence of an active petroleum system in the northern Perth Basin.

Legacy product - no abstract available

Legacy product - no abstract available