Understanding regional scale structural uncertainty: The onshore Gulf of Corinth Rift as a hydrocarbon exploration analogue

A major challenge when exploring for hydrocarbons in frontier areas is a lack of data coverage. Data may be restricted to regional scale 2D seismic lines, from which assumptions of the 3D geometric configuration are drawn. Understanding the limitations and uncertainties when extrapolating 2D data into 3D space is crucial when assessing the requirements for acquiring additional data such as 3D seismic or exploration wells, and of assigning geologically reasonable uncertainty ranges. The Onshore Gulf of Corinth Rift provides an excellent analogue for rift-scale structural uncertainty in the context of hydrocarbon exploration. Here we use seismic forward modelling to explore this area of uncertainty. Synthetic seismic sections have been generated across the rift based upon fault geometries mapped in the field. Comparison of these sections with the mapped geometries allows quantification of uncertainties encountered when extrapolating 2D data into three dimensions. We demonstrate through examples how potential column heights may be both severely over- and under-estimation due to trap integrity, spill point depth and fault seal ambiguities directly related to fault geometric uncertainty. In addition, fault geometries and linkages also control the location of hanging wall syn-rift reservoirs. Hence, gross reservoir volumes and sediment facies distributions are also significantly influenced by how fault geometries are extrapolated along-strike from 2D to 3D.