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Data-Driven Model Reduction, Scientific Frontiers, and Applications

Krishna Nunna, Harold Vance Department of Petroleum Engineering
Multiscale Reservoir Simulation Using Pressure Transient Concepts

Abstract

Fluid flow in porous media occurs on varied scales from pore to reservoir, where the fine scale heterogeneity may have a significant impact on large scale fluid flow. Resolving all pertinent scales in modeling and flow simulation is an arduous task limited by the availability of data and computational resources. Therefore, it is customary to use an upscaling procedure, in which the fine scale reservoir properties are represented on the coarse scale by some kind of averaging procedure. Existing local upscaling methods rely on steady state incompressible flow, which fail to capture transient multiscale effects especially in high contrast systems. This results in overly homogenized simulation models with systematically biased results. This same bias can be observed in multiscale flow simulation where large scale changes in pressure are resolved on the coarse scale, and multiphase fluid transport simulation is performed on the fine scale using a subgrid velocity field generated from the coarse problem. This precludes the need to upscale saturations and relative permeability which are highly non-linear and strongly dependent upon flow history. The current work combines the upscaling of pressure with multiscale multiphase simulation to generate high resolution velocity fields that capture the subgrid heterogeneity.

The local flow problem draws upon its similarity to pressure transient well testing concepts. Instead of a wellbore, each local problem is performed from a coarse cell face. This enables us to distinguish between well-connected and weakly connected pay from a coarse face. This approach is similar to the multiscale mixed finite element literature where we have a basis function for a coarse face.

The proposed method is tested on SPE10 reservoir model with over 8 orders magnitude variation in permeability making it high contrast in nature.