Modern reservoir characterization workflows attempt to integrate all available, reliable, and appropriate sources of data into 3D geocellular or numerical earth model(s). These models provide various properties such as lithofacies, porosity, permeability, hydrocarbon/water saturation at each grid cell. Reservoir simulation is then performed on the geocellular model to predict reservoir performance and production history. Geocellular models allow geoscientists to integrate various data from many different sources to calculate oil and gas volumetrics, perform efficient well planning, forecast reservoir performance, and optimize reservoir depletion schemes. In addition, within the same model, the stochastic simulation process can generate multiple equiprobable realizations, all of which honor the input data. The differences among these realizations provide a quantitative envelope of the uncertainty due to the limited reservoir information and data for the subsurface.