Matthew Balhoff |The University of Texas at Austin
Assistant Professor, Petroleum and Geosystems Engineering Cockrell School of Engineering
"Multiscale Simulation of Flow and Transport in Porous Media"
Pore-scale network modeling has become an effective method for accurate prediction and upscaling of macroscopic properties (such as permeability, relative permeability, and capillary pressure) in porous media. In many cases these models compares favorably to experimental measurements. However, computational and imaging restrictions generally limit the network size to the order of 1.0 mm3(few thousand pores). For extremely heterogeneous media these models are not large enough to capture the petrophysical properties of the entire medium and inaccurate results can be obtained when upscaling to the continuum scale. Moreover, the boundary conditions imposed are artificial; a pressure gradient is imposed in one dimension so the influence of flow behavior in the surrounding media is not included.
In this work we model single, multiphase, reactive, and non-Newtonian flow at the pore and sub pore scales but develop multiscale techniques to bridge the pore and macro-scales. A more efficient, novel domain decomposition method is used for upscaling. The medium is decomposed into hundreds of smaller networks (sub-domains) and then coupled with the surrounding models to determine accurate boundary conditions. Finite element mortars are used as a mathematical tool to ensure interfacial pressures and fluxes are matched at the interfaces of the networks boundaries. The results compare favorably to the more computationally intensive (and impractical) approach of upscaling the media as a single model. Moreover, the results are much more accurate than traditional hierarchal upscaling methods. This upscaling technique has important implications for using pore-scale models directly in reservoir simulators in a multiscale setting.