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

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.

本研究已成功利用10景ERS卫星雷达影像与4景Radarsat卫星雷达影像，完成西南海域近海海面油膜（slicks）的处理、解译与制图工作。所有油膜解译结果均已标注烃类可能性等级（hydrocarbon likelihood Level），等级范围为2至4级，其中2级为可能性最高的等级。因缺乏实际野外实测数据，本次未绘制1级油膜（详见下文第3页《油膜及其他解译术语表》）。在本次解译并制图的全部14景影像中，仅存在1处2级油膜。该重要油膜位于ERS 2 WO 01907-01轨道5883影像的西边缘区域。未提供已制图油膜的源点位置信息。通常情况下，2级油膜应提供近似源点坐标，但本次解译得到的唯一2级油膜因处于影像边缘（若有同期相邻影像，其范围大概率会延伸至邻景中），且该油膜所在海域海底深度介于2500米至3000米之间，故无法提供其源点坐标。同样，虽然3级油膜通常也应提供近似源点，但本次制图得到的2处3级油膜（与上述2级油膜同景影像）所在海域海底深度介于2500米至5500米之间，因此同样无法提供其源点坐标。按照常规规范，4级油膜无需提供源点坐标。多数4级油膜分布于近岸破波带内或其附近区域（部分可能紧邻岩质露头），此类油膜被视为假油膜，因其成因大概率与海表状态差异相关，而非烃类物质形成。