3D Modeling to Assist Subsalt Interpretation - A Case Study

Subsalt interpretation often suffers from uncertainty due to imperfection of seismic images. In this case study, the prospectivity of a deep offshore subsalt structure remained unclear after two acquisitions and several processing attempts, mainly because of the difficulty to reconcile observations from different seismic cubes. In order to address these issues, 3D seismic modelling was performed using a base case model in order to see if it was consistent with the observations made on real data. The two acquisitions were modeled and processed with the different velocity models that were used for real data migration. In comparing the results from modeling and actual data, we were able to observe that a simple model derived from our base case interpretation could generate artefacts that suggest more structural complexity. Furthermore, the visibility of a seismic anomaly according to the acquisition direction and migration model could be explained. This rather heavy process was performed in order to better constrain geometry and risk on this particular structure, and it fulfilled its objectives. With increasing computing power capabilities and an optimized workflow, this type of study could be more widely used in the near future to help interpreters facing divergent observations.