Sequence stratigraphy in the 4D-framework

The principles of seismic stratigraphy and the integration of this tool int o the 4D-procedure is discussed. A seismo-stratigraphic study has to includ e the definition of sequences and systems tracts as well as litho-facies in formation from well logs. The ultimate outcome is the final lithe-model, wh ich may serve as input to define flow units as well. Since seismostratigrap hy is an interpretive tool, as additional step the consistency of the resul ting lithe-model (in terms of the existing seismic data used to build it) i s checked by forward modelling: this step is called the Verification Loop. It implies that the resulting lithe-model in depth-domain is mapped onto a fine grid (e.g., 2 x 2 meters) and subsequently is forward-modelled in pres tack or poststack, acoustic or elastic mode. The modelling result (i.e., wa vefields!) has to be migrated and subsequently compared back to the actual seismic data. This process is an iterative process, where usually two itera tions suffice. It is evident that this step in its resolution power depends on the seismic bandwidth available. Two case histories are given, addressi ng carbonate and elastic reservoirs.