TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractDiagnosis, characterization and modeling of high permeability layers constitute a very challenging issue while building carbonate reservoir models for flow simulation.In karstic reservoirs, the evaluation of the dual permeability behavior is the key to assess reservoir heterogeneity. This heterogeneity is expressed by highly variable and non-stationary reservoir properties. The 3D organization of these reservoir properties depends on the parameters, which drove the karst development (fracture network, sequence stratigraphy, hydraulic gradient).This paper presents an integrated methodology for the evaluation of the karst network and its 3D modeling in single porosity models.In a Middle-East reservoir, a synthesis of dynamic data shows a clear dual porosity/permeability behavior, which is explained both by the core description and the well test interpretation.The karst network is proved to be driven by an early diagenesis along sequence boundaries. The 3D organization of the karst network is assessed from the integration of sedimentological/structural models and dynamic data.Fine gridded models are achieved before the full field simulation to evaluate matrix-drains exchanges. Results from these sensitivity models enable to input realistic reservoir properties in the coarse full field. A methodology for preservation of dual permeability behavior through downscaling process is presented.The reservoir layering is defined in order to preserve the key heterogeneity in the coarse model, moreover, homogeneous equivalent petrophysical parameters are assigned to high permeability layers. A specific modeling of permeability, saturation and Rock-type in karstic layers is performed.The matching of the production history is obtained without any drastic changes in reservoir properties; that confirms the distribution of the karst network. SPE 78534Karstic high permeability layers: Characterization and Preservation while modeling carbonate reservoirs Roselyne BOTTON-DUMAY, Thierry MANIVIT, Gérard MASSONNAT, Viviane GAY, TOTAL FINA ELF

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