SEISMIC STRATIGRAPHIC INTERPRETATION OF DEEP-WATER DEPOSITIONAL SYSTEMS CONSTRAINED BY ELASTIC WEDGE FORWARD MODELING

Predicting sedimentary fairways, distribution and quality of reservoir in a frontier play like deep-water offshore Nova Scotia is a challenging task. Exploration risk is reduced only by an interpretation process that integrates multiple data sets and approaches and by making use of technologies best suited for a given geologic problem. The presentation will address the methodology for predicting and understanding deep-water fairways in offshore Nova Scotia using a seismic stratigraphic approach, i.e. identify and map seismic packages based on reflection terminations (onlap, toplap, downlap, baselap etc.) and reflection configuration (parallel, sigmoidal, chaotic etc). Sedimentary facies, depositional environments and architectures are then interpreted for each of the facies and a well-log based seismic forward modeling is used to constrain this interpretation. The advantages of using this approach are: (1) we attempt to validate a geologic model by comparing the existing seismic with a data-constrained seismic model; (2) we build a seismic forward model that is consistent with the actual rock properties; and (2) we attempt to calibrate the seismic response to show changes in lithology, net-to-gross, sand percent, porosity, fluid type. For the specific Cretaceous system in deep-water Nova Scotia for which we made seismic forward models, we find diagnostic responses from sequence boundaries where the best quality sands have adjacent regional shales. We have the least diagnostic responses from silt-prone facies, regardless of adjacency. Internal reflectivity related to expansion of the reservoir interval seems to offer the most hope for robust and predictive seismic evaluation.