We utilize Synthetic Aperture Radar (SAR) images to detect naturally occurring oil seepage in deep and ultra-deep waters, and in untested offshore frontier basins. This technique led to the development of our Global Offshore Seeps Database (GOSD) and its incorporation into Seep Explorer, which has rapidly become the industry standard with support from the majority of the world’s oil companies.
The early detection of active oil and gas seeps in frontier or under-explored basins can greatly reduce exploration risk by establishing both the presence of a mature source and, by inference, the existence of oil and gas accumulations (from which the seeps originate).
Our SAR seepage detection technique maps slicks on the ocean surface, which are then interpreted and categorised into a number of confidence categories. The interpreted oil slicks form the basis of the Global Offshore Seepage Database (GOSD), which is instantly available for 90% of the world’s offshore basins.
We have been developing the database since 1992 through combined experience that is unrivalled in this field. The principal benefits of satellite SAR are that it provides low cost, multi-pass, non-interventionist global coverage, and therefore provides valuable indication on source presence ahead of any exploration commitment.
SAR seepage detection is reliant on oil accumulations moving along migration pathways to the seafloor, where it will form either liquid oil bubbles or a film on gas bubbles. These bubbles transport the oil to the sea surface where they burst and leave behind a thin oil film ‘pancake’. Over time these pancakes coalesce and form slicks.
Detection of slicks from SAR relies on the damping properties of oil on the capillary waves (mm to cm wavelength range) that populate the sea surface at low to moderate wind speeds. It is therefore imperative that only scenes fulfilling these criteria are used in the process.
Areas of the sea surface where waves have been suppressed by oil (or organic material) do not return radar energy to the satellite (backscatter reduction), and these areas appear black or dark on the processed imagery.
The characteristics of the slicks and their repetition over time allow us to classify their origin. Interpretation of imagery and the categorization of the slicks requires a high level of experience in this domain, of which ours in unparalleled.
Data is collected using several different SAR satellites: ERS-1 & -2, Envisat, Sentinel-1, ALOS, RADARSAT-1 & -2, TerraSAR-X and COSMO-SkyMed. SAR observes the ocean surface day and night and is largely unaffected by all but the densest clouds. Seep Explorer was recently launched following the acquisition of GLOGOS (Global Onshore Gas-Oil Seeps data set), from Gas Consult and the combination of CGG’s existing seepage data from NPA’s GOSD (Global Offshore Seepage Database), Robertson’s Frogi seeps layer and NPA’s recently created FFD (Fluid Features Database) of fluid escape features.
We offer a comprehensive seep detection workshop and bespoke training for offshore SAR interpretation.
The seepage detection workshop provides a comprehensive overview of the science and technology underpinning the detection and mapping of surface oil slicks and its application to oil exploration. This workshop aims to satisfy four key objectives:
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