Report on the Interpretation and Mapping of Natural Hydrocarbon Seeps and Other Features on the South West Margins Off the Western Australian Coast using Satellite Radar Data

Brief description

The processing, interpretation and mapping of slicks offshore of the South West Margins using ten ERS satellite radar scenes and four Radarsat scenes has been completed successfully. All slick interpretations have been attributed with a hydrocarbon likelihood Level ranging from Level 2 to Level 4 with Level 2 being the most likely. Given the absence of actual field data, no Level 1 slicks have been mapped (see Glossary of Slick and Other Interpretations, p3 below). For all the fourteen scenes interpreted and mapped, there is only one Level 2 slick. This significant slick is located on the western edge of scene ERS 2 WO 01907-01 Orbit 5883. No locations have been provided of the sources of mapped slicks. Although an approximate point source would normally be provided for Level 2 slicks, the only Level 2 slick mapped (as above) is not complete as it is on the edge of the image (and presumably would continue on to an adjacent image acquired at the same time if it were available) and given the depth to sea floor of between 2,500m to 3,000m, it is not possible to provide a point source. Likewise, while an approximate point source would normally be provided for Level 3 slicks, given the depth to sea floor in the locations of the two Level 3 slicks mapped (same scene as for the Level 2 slick) of between 2,500m to 5,500m, it is not possible to provide a point sources. As per normal, Level 4 slicks are not provided with a source point. Many of the Level 4 slicks are located along the coastline in or near to the surf break zone (some possibly adjacent to rocky outcrops) and as such are regarded as false slicks as they most likely relate to differences in sea surface conditions and not to the formation of hydrocarbons.

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