Geophysical Characterization of Shallow Fluid Flow and Gas Hydrates in the Southern Kwanza Basin, Offshore Angola - Implication for Hydrocarbon Migration and Thermal Modeling

Abstract

Dedicated: Fluids & Flow - Studies of shallow fluid flow phenomena along the Angolan margins have revealed the widespread occurrence of past and present fluid flow phenomena in the Lower Congo Basin and to a lesser extent in the Kwanza Basin. Detailed mapping of fluid flow phenomena in the southern Kwanza Basin have highlighted the presence of seep related features including pockmarks, mud volcanoes, gas hydrate pingoes and bottom-simulating reflection (BSR). The distribution and intensity of fluid flow features are largely controlled by the tectono-stratigraphic framework characterizing the contractional domain along the Angolan continental margin. Salt re-mobilization have played an important control as shown by the presence of salt diapirs directly associated with the occurrence of mud volcanoes and gas hydrate pingoes, as opposed to salt nappes over which both the overburden and seafloor appear featureless. BSR depths, corresponding to the base of the gas hydrate stability zone (GHSZ), have been use to estimate shallow geothermal gradient and highlight thermal anomalies related to highly conductive salt and warm fluid advection along focused fluid flow pathways. All in all, fluid flow studies are a useful tool to better understand the properties and dynamics of sedimentary basins while considering hydrocarbon migration and thermal modeling.