Once these strata or layers are identified, the distribution of channel complexes versus overbank deposits within each strata represents second order heterogeneities. The distribution of individual channels within each channel complex constitutes third order heterogeneities. Sequence stratigraphy allows such hierarchical classification of heterogeneities down to the bed set or bed level. This genetic hierarchy of heterogeneities within a given reservoir is best modeled through a hierarchical procedure. A hierarchical object-based procedure was applied to model the channel sand distribution in each layer. The key geologic input parameters are (1) the proportion of channel sand that could vary vertically and areally, (2) geometric parameters defining the channel thicknesses, widths, and sinuosities, and (3) well data. In this case, the layer proportions were assumed constant, realistic channel geometries were considered, and no well data were used to constrain the model. The second panel of Figure shows a cross section through the channel and overbank shale facies model.