INTEGRATING MULTIPHASE PRODUCTION HISTORY IN STOCHASTIC RESERVOIR CHARACTERIZATION

This paper focuses on integrating field-production history into reserv oir characterization through stochastic inverse modeling. A key elemen t of our approach is a three-dimensional (3D) streamline simulator tha t is orders of magnitude faster than traditional numerical simulators and thus allows for rapid inversion of multiphase production data. Sto chastic permeability fields, conditioned to field-production history, are then generated with simulated annealing. We also explore the spati al resolution associated with estimates of reservoir permeability vari ations derived by use of field-production history. On the basis of tec hniques from geophysical inverse theory, we address such issues as dat a sensitivity, spatial resolution, averaging kernels, and uncertaintie s associated with our estimates of reservoir permeability. The propose d inversion technique has been applied to synthetic as well as field c ases. The synthetic example involves a sensitivity analysis of multiph ase production history in heterogeneous five-spot and nine-spot patter ns. The field example consists of production history from a five-spot pattern in the north Robertson unit, a low-permeability carbonate rese rvoir in West Texas. Watercut history at the producers are used to est imate permeability variations in a two-layer (matrix-fracture) model o f the reservoir. All computations were performed on a 125 MHz Pentium with an average run time of about 4 wall-clock hours, indicating the f easibility of our approach.