Combining Velocity Model Building and Interpretation Techniques to Reduce Uncertainty in Pre-salt Imaging

There is ever increasing interest in exploring pre-salt provinces across the South Atlantic Conjugate Margin The 2006 discovery of the Lula (Tupi) field in the Brazil Santos Basin and more recent discoveries such as the 2012 Azul Field in the Angolan Kwanza Basin in the Lower Cretaceous, have proven that there is a working hydrocarbon system across the South Atlantic Conjugate Margin. The key to evaluating the prospectivity of these pre-salt provinces is generation of an accurate seismic image using pre-stack depth imaging methods. However, it is not possible to obtain a useable image below allochthonous salt using an approach entirely dependent upon algorithms to construct the PSDM velocity model. The introduction of geological understanding through seismic interpretation, basin modelling and the (limited) available well data can aid PSDM velocity model accuracy and reduce uncertainty of the pre-salt image obtained (Merry, 2012). This paper reviews an approach taken to resolve the pre-salt image using data examples from Angola Blocks 24 and 25.