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Confirming the Presence of a Working Petroleum System in the Eastern Black Sea Basin, Offshore Georgia Using SAR Imaging, Sea Surface Slick Sampling, and Geophysical Seafloor Characterization


As new plays emerge in deepwater settings, one of the more difficult tasks facing the explorationist is to find evidence confirming the presence of a working petroleum system. In the Eastern Black Sea Basin, the elements of a petroleum system are likely present. Source rocks of Oligo-Miocene age in the Maykop Formation should be charging Middle Miocene deepwater channel-levee sands in fold and thrust system traps. But to reduce the exploration risk in this frontier area, direct evidence of hydrocarbon generation and migration is needed. To provide confirmation of charge, a collection of diverse data was used. First, synthetic aperture radar satellite images revealed the presence of large recurring sea surface slicks over prospective structures. These slicks were then sampled during 3-D seismic data acquisition. Geochemical analysis showed the compositional characteristics of the slicks’ hydrocarbons were similar to known Maykop sourced oils in the region. To verify that the slicks were related to the subsurface, a seafloor extraction from the 3-D seismic data was used to identify bathymetric features consistent with seafloor hydrocarbon seepage. The features identified included pockmarks, near seafloor sediments with high impedance contrast suggesting authigenic carbonates, and mud volcanoes. The apparent origins of the slicks on the sea surface were found to be coincident with the locations of these seafloor features. And finally, the 3-D seismic imaging was used to demonstrate there are potential migration pathways from the suspected charged traps to these seafloor features. This combination of data provides a high level of confidence that the seismically imaged traps in the Eastern Black Sea Basin in offshore Georgia are charged. What it cannot tell us is how much petroleum may be in these structures. This question can only be answered by the drill bit.