Seismic and acoustic imaging of fluid seepage structures in different sedimentological and tectonic settings in the Lower Congo Basin

Abstract

Using various geophysical methods including multichannel seismics, bathymetric mapping and sediment echosounding, several active gas seepage sites on the seafloor in the deep Lower Congo Basin were investigated. Gas is formed within Oligocene to Miocene fan deposits and relies on migration pathways to reach the seafloor. To the South of the Congo Canyon, continued seaward moving deformation induced by Aptian salt movement is shown to promote active gas seepage at the deformation front while further landward sites remain inactive. In the vicinity of the post-Miocene Congo Fan to the North of the Congo Canyon, active seepage can be shown to depend on salt tectonic faulting that connects gas-charged Pliocene fan deposits to the seafloor in the absence of widespread polygonal faulting in hemipelagic sediments. These investigated seepage sites act as an example of possible gas seepage configurations at the front of compressional regimes that can be applied to other similar areas.