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About the connectivity of dual-scale media based on micro-structure based regional analysis of NMR flow propagators

Zheng, Yong, Shikhov, Igor, Gbayan, Louis Kpamsar, Arns, Ji-Youn, Arns, Christoph H.
Journal of contaminant hydrology 2018 v.212 pp. 143-151
image analysis, mathematical models, microstructure, nuclear magnetic resonance spectroscopy, porous media, tracer techniques
The characterisation of heterogeneous porous media at multiple length scales typically requires the classification of structure at some scale to allow the calculation of effective transport properties at a scale relevant for macroscopic description. While such a classification may be derived from various imaging methods, a shortcoming is often the simultaneous characterisation of the connectivity between regions representing different micro-structure. In this work we combine NMR based flow propagators with the simulations performed on corresponding reconstructed structure, and relate the NMR measurements to their simulated global and local representations to study fluid transport locally and the exchange between micro- and macro-porous regions. This is achieved by carrying out detailed lattice Boltzmann simulations and random walk method to track the displacements of tracers in each kind of region. Using Euclidean distance maps (EDT) we analyse the fluid invasion to regions of different scale and relate it to the connectivity of the system. We demonstrate that numerical simulation has great flexibility in providing additional sensitivity to the inference of region-region connectivity.