Accurate coarse modeling of well-driven, high-mobility-ratio displacements in heterogeneous reservoirs

Abstract

High mobility ratios are often encountered in improved-oil-recovery processes because the displaced oil can be much more viscous than the injected water or gas. In this work, a new two-phase upscaling approach for modeling high-mobility-ratio displacements is developed and applied. For the near-well region, a specialized upscaling procedure, which includes single-phase and two-phase upscaling components, is presented. In this upscaling, local regions around each well are considered and the coarse-scale well indices, wellblock transmissibilities, and relative permeabilities are determined such that the fine- and coarse-scale flow rates are in agreement. Away from wells, the upscaled relative permeabilities for each coarse block are computed by imposing effective flux boundary conditions, which have been shown to provide better accuracy than standard procedures. The performance of these techniques is demonstrated by considering multiple realizations of synthetic 3D models with varying correlation structures and degrees of spatial variability, as well as different fluid mobility contrasts and production scenarios (involving horizontal wells and five-spot patterns). By quantifying the upscaling errors using well-defined metrics, the contribution of each component of the overall procedure to the accuracy of the coarse models is assessed. Application of the overall upscaling methodology is shown to provide significantly more accurate coarse models than those generated using standard procedures.