Digital outcrop model of deepwater clastic wedges onlapping salt ridges (Bay of Biscay): 3D seismic modeling applied to North Sea reservoirs

Three-dimensional digital outcrop models are more reliable analogues for reservoir modeling compared to 2D photos or morphometric parameters of modern systems. Virtual outcrops are suitable for generating synthetic seismics, bridging the gap between outcropping depositional facies and seismic facies derived by a forward modeling-inversion-classification workflow. An airborne texturized Lidar survey was acquired along large coastal cliffs of Bay of Biscay exposing a thick Albian succession. The survey shows deepwater wedges affected by progressive unconformities flanking salt ridges, where breccias and debris flows fed by the underlying carbonates are onlapped by siliciclastic turbidites. The resulting geomodel was converted in 3D synthetic seismic volumes via petro-elastic relationships derived by subsurface analogue datesets. A seismic inversion process was performed to check how much of the original features are restituted by seismic modeling and to assess the optimal attributes for different stratigraphic, geometric and litho-fluid constraints. The synthetic seismics provides the imaging of progressive unconformities and a good match between sedimentary facies and seismic/impedance facies. A remarkable similarity exists with a Thanetian deepwater reservoir (Forties Fm) confined by the Oselvar diapir in Southern North Sea, where mud-supported debris flows reworking Upper Cretaceous chalk debris interfinger with the Forties distal lobes onlapping the diapir flank.