Finite Difference Modelling Applied to 3D/2D Walk-away VSP to Assess Carbonatic Reservoir Geometry Uncertainty

Here we present a work done for the Zohr giant gas field PSDM project. The reservoir is in a Cretaceous carbonate platform located below a structurally complicated salt body. Despite the application of the most accurate imaging algorithms, in some areas the interpretation of the top of the carbonate platform remained extremely complex and uncertain, calling for a better understanding of the potentialities of available data. When dealing with complex geological settings such as salt, carbonate platforms, etc., the deep understanding of the illumination provided by the data acquired on the field is of outmost importance. In such cases, a conventional illumination analysis that uses ray-based tools is not advisable and wave equation-based or finite difference modelling algorithm should be favoured. Different VSP acquisition geometry illumination tests were performed, searching an optimal solution for sub-salt imaging enhancement.