 |
Center for Nonlinear Studies |
Direct numerical simulations of flows through explicit pore spaces are providing unprecedented insights into how pore wall geometry and pore network topology influence flow and transport therein. X-Ray tomography provides high-resolution three-dimensional images of pore-spaces that can be used in these simulations. However, the use of these pore-space images is limited by the availability of rock samples and the cost of imaging. An alternative approach to using imaged pore samples are stochastically generated realistic pore spaces with prescribed geometric and topological properties. These virtual pore spaces are easily generated and allow for the thorough investigation of how variations in the pore structure influence flow and transport. We stochastically generate realistic three-dimensional pore-spaces using a novel thresholding method, and then the flow of an isothermal single-phase fluid through these explicit pore spaces is computationally determined. The resulting steady state non-uniform fluid velocity fields are analyzed using particle tracking, finite time Lyaponuv exponents, and upscaling to relate them to the pore-space. Although the pore-spaces are isotropic with no preferred direction of flow, the fluid dynamics within them span a wide range of behaviors. Areas of stagnation occur along side regions where neighboring fluid particle trajectories separate rapidly. The structure of the heterogeneous flow fields is related to the pore-space geometry and topology. Particular focus is placed on how the pore network influences transport. This research was done in collaboration with Carl Gable and Scott Painter at Los Alamos, and Larry Winter at the University of Arizona.