Enhancing Prospectivity by Integrating Satellite Seep Data with 3D Seismic, Lower Congo Basin

Multiple pass satellite SAR data offshore Angola integrated with interpreted 3D seismic data from the Lower Congo Basin has revealed many locations where repeat seeps overlie clearly defined hydrocarbon escape features, as defined by shallow amplitude anomalies on seismic data. The correlation of high ranked slicks and the distribution of salt diapirs and pillows is striking. Moreover, correlation of the satellite seeps with the prognosed post-salt source kitchen (Iabe Fm) provides further validation of the link between reservoir, trap and sea-bed/sea surface observations and helps to explain several dry wells drilled in migration shadows. This area of dense seepage in the Congo Fan is in sharp contrast to the much reduced satellite seepage observed in the successful subsalt plays in the Kwanza Basin; the reason being that the main pre-salt source (Bucomazi Fm) is mature in this basin whereas the post salt source is not, so the oil has had to migrate from deeper intervals and can only escape through a limited number of areas where the salt is thin, absent or completely withdrawn. Other West African examples from Angola and Gabon will be shown which also demonstrate the link between slicks and seepage manifestations observed on 3D seismic data.