Abstract
Upscaling is often applied to coarsen detailed geological reservoir descriptions to sizes that can be accommodated by flow simulators. Adaptive local-global upscaling is a new and accurate methodology that incorporates global coarse scale flow information into the boundary conditions used to compute upscaled quantities (e.g., coarse scale transmissibilities). The procedure is iterated until a self-consistent solution is obtained. In this work, we extend this approach to three-dimensional systems and introduce and evaluate procedures to decrease the computational demands of the method. This includes the use of purely local upscaling calculations for the initial estimation of coarse scale transmissibilities and the use of reduced border regions during the iterations. This is shown to decrease the computational requirements of the reduced procedure by a factor of about six relative to the full methodology, while impacting the accuracy very little. The performance of the adaptive local-global upscaling technique is evaluated for three different heterogeneous reservoir descriptions. The method is shown to provide a high degree of accuracy for total flow rate, local flux and oil cut. In addition, it is shown to be less computationally demanding and significantly more accurate than some existing extended local upscaling procedures.
