A remote sensing study aimed at identifying location(s) of natural oil seeps in 300 to 3,000 m water depths in the offshore Campos, Santos and Espírito Santo basins of Brazil has been conducted by Geochemical Solutions International Inc. (GSI). This study applies seep detection methodologies in support of offshore exploration in the marginal basins of Brazil.
Natural oil and gas seeps have historically provided invaluable information to oil explorationists. Foremost, they indicate the presence of generative hydrocarbon source rocks, without which there can be no accumulations. The high cost of offshore exploration has made the identification of seeps a well-accepted risk assessment methodology. RADARSAT-1 is the best spaceborne remote sensing technique for detecting ocean surface features in frequently cloud-covered marine areas such as the Espírito Santo, Campos and Santos basins offshore southeastern Brazil. However, with regard to radar imaging, the suppression of the wave backscatter is unfortunately not unique to the presence of oil. False targets include wind shadow, natural surfactants, local upwelling, shallow marine vegetation, and areas of heavy rainfall. Our approach circumvents these pitfalls using a proprietary textural classification algorithm than enhances ocean surface features related to natural and man-made oil slicks in RADARSAT-1 data.
Historical databases obtained by other satellite systems, such as the Advanced Very High Resolution Radiometer (AVHRR), have been similarly analyzed and areas of smooth texture on the RADARSAT-1 images not related to oil slicks disregarded. The remaining regions have then been combined with seismic (published structure-contour maps of top of salt) and bathymetry data in order to identify the loci of natural hydrocarbon seepage and to infer possible migration pathways from the reservoir to the sea floor.
This program was initiated on 15 July 1998 and is complete and ready for immediate delivery. The data products consist of (1) graphic image files and maps showing locations of interpreted natural oil seeps overlaid on hybrid color composites and IHS combinations of geophysical (depth to top of salt) and bathymetric data in raster format, and (2) regional maps showing the location of seeps in the tectono-stratigraphic context of the Espírito Santo, Campos and Santos offshore basins. These can be distributed both on printed media as well as on a CD-ROM.
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