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Regional Prospectivity, Offshore the Republic of the Congo

Abstract

The merge of several 3D post stack seismic surveys offshore Republic of Congo covers a total area of over 21,000 sq km, showing geological features on a regional scale. Several plays and trends are revealed and leads have been identified within the survey-merge. This study distinguishes among four different play types: 1, Upper Miocene channel systems; 2, Lower Miocene turbidite channels; 3, Sendji Carbonates and; 4, Pre-salt sandstones. The geological development of all plays is associated with the separation of the African and South American plates during the Late Jurassic which can be subdivided into four distinct phases of deposition and deformation; Pre-Rift, Syn-Rift, Post-Rift deposition, and salt tectonic deformation. The Miocene plays are sitting in channels where sedimentation geometry is controlled by the topographic basins situated between the anticlinal structures above the salt walls. A Root Mean Squared (RMS) amplitude extraction within a 100ms time interval in the Upper Miocene shows the details of multiple “meander-form” channel systems extending from the Congo River Delta, traversing the deep basin and terminating in fan shaped morphologies. These channels and fan systems trend roughly SE to NW and the amplitude extraction illustrates the depositional system of sandbodies, which clearly stand out as high amplitudes. The regional interpretation of these features provides information on paleocurrent direction, flow changes over time as well as the displacement of channel systems due to tectonic activity and salt domes. There have been several discoveries within these meandering systems and the regional scale of this RMS map allows the identification of additional leads within the same channel system. The Albian Carbonate play (Sendji Formation) is controlled by the movement of salt in the current shelf area, which created traps within turtle back and anticlinal structures, whereas the pre-salt plays (sandstones) are either trapped structurally by the salt and normal faults or stratigraphically by pinching out updip towards the basement and the salt. The regional coverage of the Congo MegaSurvey allows the interpreter to identify and locate prospects over a wide area. These play types present excellent hydrocarbon potential. Additionally, discoveries from adjacent Gabon and Angola can be considered as analogues and can provide further information about the hydrocarbon potential in the less explored Republic of Congo.