An optimization method for incorporating dynamic data into reservoir modelling is presented. It integrates a very typical feature of the zonation approach that is based upon dividing the reservoir model into subregions. Solving the optimization problem consists of adjusting the subregion pattern so that the reservoir model duplicates the observed dynamic behaviour. Unlike the traditional approach, permeabilities in subregions are not constant, but show spatial variations. A variogram model that is the same for all the subregions describes this variability. The suggested method allows for optimization of permeability distributions within the subregions while preserving the second-order statistics for the whole reservoir model as well as the spatial continuity between subregions. It remains as flexible as the traditional zonation approach although it can handle complex structures.