An accurate reconstruction of reservoir heterogeneity is an important goal of a reservoir study. The methodology presented here is aimed at providing a complete petrophysical characterization of the reservoir, particularly when the heterogeneity cannot be adequately described using traditional methods. The first phase of the methodology is integrated petrophysical characterization. This is performed by a statistical analysis of log and core data using a 'cluster analysis' algorithm. This allows an objective classification of the reservoir components into homogeneous subsets (lithofacies), each with specific lithological and petrophysical characteristics. The second phase is simulation of the reservoir heterogeneity. Here, the 3D distribution of the lithofacies recognized at the wells is performed consistently with the sedimentological model by means of geostatistical simulations carried out using a high-resolution grid. The porosity and permeability values characterizing each lithofacies are then assigned to the simulated images to obtain a highly detailed 3D petrophysical description of the reservoir.