Miscible gas injection offers both high local displacementefficiencies and a means for handling produced gas. As finescale simulations of miscible processes can be very timeconsuming,there is a clear need for an accurate and robustcoarse scale miscible simulation capability. In this paper, wepresent a new upscaling technique for the accurate coarsescale simulation of first-contact miscible displacements. Ourmethod contains two key components: Effective FluxBoundary Conditions (EFBCs) and the Extended Todd &Longstaff with Pseudo relative permeabilities (ETLP)formulation. EFBCs, which were applied previously within thecontext of immiscible displacements, account approximatelyfor the effect of the global flow field on the local upscalingproblems and as a result mitigate inaccuracies introduced bystandard procedures. The ETLP formulation modifies the wayeffective fluid properties and upscaled relative permeabilitiesare computed in a limited compositional framework such thatresidual oil that is immobile and unavailable for mixing isefficiently represented.The accuracy of the new technique is demonstrated forseveral example problems. Using synthetic models withdiffering permeability correlation lengths, we show that thenew method provides results superior to those obtained usingexisting upscaling procedures (standard upscaled relativepermeabilities, upscaled absolute permeabilities only, andnonuniform coarsening) for partially layered cases. Thebreakthrough time, oil production curve and saturation profilesare predicted accurately. The method is also shown to performwell over a wide range of coarsening factors (4 – 2500) forseveral fields with different permeability heterogeneitystructures. Finally, we apply the method to a real field casewith encouraging results, indicating the practical applicabilityof the new technique.
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