A permeability model was developed for a thin valley-fill reservoir at Postle Field, Oklahoma, with the objective of increasing the accuracy of flow simulation. The presence of high-permeability zones that are below seismic resolution represented the greatest challenge to overcome. This challenge is common as the average reservoir thickness in North America is 17 ft (5 m). Enhanced oil recovery is underway at Postle Field to increase production and to revitalize the field. The process involves carbon dioxide flooding which is fast becoming the dominant mechanism of Tertiary recovery. To optimize the recovery efficiency of this process, it is important to understand the influence of permeability heterogeneity and its role on fluid flow. High-permeability zones have the potential to cause early breakthrough and poor sweep efficiency.