Numerical simulations of sedimentation and compaction of turbiditic sand at reservoir scale in the Peïra Cava sub basin

The deterministic software MassFLOW-3D™ has been successfully used to construct a 3D model for the simulation of turbidity currents and predict bed geometry and grain size distribution in a single bed (Marker Unit 5) from the deep-marine Peïra Cava basin (Eocene-Oligocene Annot Sandstone, SE France). The first stage of the modeling was to recreate the pre-MU5 bathymetry onto which the MU5 bed was deposited. This was done with four composite flow events starting from the base reconstructed surface with subsequent modelling of compaction and isostatic bending after each flow. The cumulative deposited thickness of the four flows matched the observed thickness in the control points. In a second phase the simulation of the MU 5 bed, starting from the so-recreated surface, was performed. Four grain sizes were used for the simulation: 80 μm (35% concentration), 200 μm (35% concentration), 400 μm (20% concentration) and 1 mm (10% concentration), as suggested by the available data-points. There was a reasonable match between the observed and modelled grain size distributions and thickness. We suggest that such an approach could form a part of a probabilistic workflow and be used to capture likely ranges of parameters for improved exploration and reservoir management.