Evaluation of 3D Seismic Data and Interpretation of Mars Field Offshore Dahomey Basin Nigeria

Abstract

Abstract: 3D seismic interpretation of the Mars Field in the Dahomey Basin, Nigeria was done to delineate the
lithostratigraphy, structures, seismic stratigraphy and mapping of potential reservoirs within the basin. This was achieved by
the use of 4 wells and 3D seismic data. This study determines the structural style, stratigraphic units, unconformities, channels,
clinoform, structural framework, time, and depth maps of the potential reservoirs. The fault within the field is normal fault, and
the hydrocarbon trapping styles are four-way closures and fault assisted closures. The local stratigraphy reveals that presences
of the basement, erosional surfaces, topset and bottom set of the prograding clinoform. The faulting within the basin affected
mainly the pre-rift sediments which are the Albian Carbonates, while the Cretaceous sediments are syn-rift sediments. The
hydrocarbon bearing reservoir units are the Turonian reservoirs, which were correlated and mapped across the 3D seismic
section. The hydrocarbon contact was used on the depth map to delineate the fluid contact on the map. The seismic interpretation
was carried out to delineate the structural style of the basin. The fault was mapped as normal fault using inline and variance
time slice. The structural framework was generated to understand the geomorphology of the Late Cretaceous sediments which
reveals the degree and the effect of the unconformity on these sediments showing that some part has been completely eroded.
The trapping style in the field is faulted anticlinal closure. The fault has therefore offset the continuity of the reservoirs thereby
juxtaposing the reservoir beds (sands) with non-reservoir beds (shales) essentially trapping hydrocarbons. The Cretaceous
sediments are the major hydrocarbon reservoir within the basin and four hydrocarbon bearing reservoir maps were generated
to show the hydrocarbon distribution within the basin.

Keywords: Dahomey/Benin basin, depth map, time map, local stratigraphy, fluid distribution map, clinoform, Turonian.