The characterization of invisible hydrocarbon micro-seepage intensities in surface sediments is used to evaluate subsurface hydrocarbon potential. A cost-effective multidisciplinary surface prospecting method, termed "BIG", is employed as a supplementary instrument to conventional exploration tools to assess the remaining prospectivity of a licence tract in the Dutch North Sea. Microbial investigations, molecular and isotopic gas characterization as well as UV fluorescence measurements are utilized for direct hydrocarbon detection in surface sediments. The definition and distribution of anomalous intensities is used as an index for the hydrocarbon potential in the deeper sub-surface. In combination with seismic information the BIG method can help to reduce exploration risk. It proves to be an effective instrument to determine the lateral extent of liquid hydrocarbon migration and to localize areas of prospective potential. This case history covers a successful application of the BIG method to investigate undetected hydrocarbon potential in an established producing province.

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