Scaleup of Geological Facies for Multiphase Flow Simulations

Abstract A major challenge in understanding and predicting the performance of petroleum reservoirs is to describe their geologic and their petrophysical heterogeneities realistically and to represent the described heterogeneities in a reservoir simulation model. Detailed and realistic reservoir models usually incorporate several geologic facies or lithotypes, each exhibiting unique relative permeability and capillary pressure characteristics which must be accounted for during numerical simulations. This paper describes a steady-state methodology to generate effective multiphase flow functions (relative permeability and capillary pressure) and pseudo functions for reservoir models consisting of multiple geologic facies. The generated effective flow functions capture the variations in geologic facies and petrophysical heterogeneities that control reservoir performance. The technique can be used to scale up complex geologic models for reservoir simulators. This steady-state approach is significantly faster than other techniques requiring multiphase flow simulations. The technique was applied to scale up a realistic 3-D reservoir description of a complex fluvio-deltaic sandstone reservoir. The generated effective flow functions were used successfully to reproduce truth case' performance predictions (oil recoveries, pressure profiles, and water production) for a quarter 5-spot and a quarter 9-spot pattern. The generated effective flow functions depend largely on the permeability distribution, the spatial distribution of geologic facies, and the relative proportions of the geologic facies in the reservoir model. P. 301