Seismic Modelling of the Stratigraphic Architecture of Syn-rift Gilbert Delta Bottomset and Deepwater-fans of the West Xylokastro Fault Block, Corinth Rift

The stratigraphy of rift basins records complex interactions of earth surface processes, palaeoclimate, and tectonics in active margins, and in some regions, hosts important hydrocarbon reservoirs and potential CO2 storage sites. Nevertheless, coarse-grained syn-rift deep-water depositional systems remain relatively poorly understood and are not well documented in the literature. Detailed characterization of accessible outcropping systems like these is necessary to improve understanding of stratigraphic architecture and depositional processes, which can have direct applications towards estimation of hydrocarbon volumes, reservoir architecture and potential traps in the subsurface systems. This study aims to investigate the seismic expression of deep-water syn-rift depositional systems by generating 2D synthetic seismic images through the 2(3)D point spread function convolution method from two digital outcrop analogues composed of syn-rift Plio-Pleistocene Gilbert-delta bottomset and deep-water fan deposits from the Gulf of Corinth, Greece. The application of 2D seismic modelling of well-constrained outcrop architectures can help constrain the typical seismic signature related to depositional elements of these systems, which can be used to predict possible sub-seismic heterogeneity/ geology. By interpreting these virtual outcrop models, in combination with previous field observations, down to bed and bed-set scales, realistic geological models are constructed to be used as input for the seismic modelling. The geological models are assigned elastic properties (velocity and density) obtained from well data from an analogous subsurface setting in the Norwegian Sea, The Fenja Field, allowing for seismic modelling with realistic subsurface elastic properties. The results in this study reveal that the seismic expression of the architectural elements appears relatively simplistic in the seismic images, however, the complex heterogeneity of these deposits will generate subtle amplitude variability affecting the resulting seismic. The dominant frequency is the geophysical parameter influencing the resolution of the 2D seismic images the most, where low-resolution seismic (20 Hz) images only the significant changes in dominant lithologies, whilst high-resolution seismic (140 Hz) exposes a higher amount of the internal heterogeneity. The outcome of this study illustrates that the key architectural elements of the deposits within these systems will, in many instances, fall below seismic resolution, hence, a depositional element interpretation would require integration of well-based observations from core or wireline in the subsurface to place confidence on depositional element interpretation.