TITLE:
Solving Diffusion Time in Heterogeneous Microscale Rock Matrix by 3D Computations: Non-Fickian Dispersion Observed in Porous Media
AUTHORS:
Khalil Abou-Saleh, Jalal Dweik, Youssef Haidar, Abbas Ghaddar
KEYWORDS:
Matrix Diffusion, Time Domain Random Walk, Memory Function, Mobile-Immobile Mass Transfer
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.7 No.12,
December
16,
2019
ABSTRACT: Understanding and simulating the
underlying microscopic physics of the rock matrix is very useful for
determining macroscopic physical properties such as permeability. Matrix
diffusion is an important transport parameter controlling the late-time behaviour of breakthrough curves (BTCs). We compute the memory function, implemented in the sink/source term of
Mobile-immobile mass transfer by solving the matrix diffusion using a time
diffusion random-walk approach. The diffusion is controlled by different
parameters like the porosity, tortuosity, mobile-immobile interface and
immobile domain cluster shapes. All these properties are investigated by X-ray microtomography that
captures the main characteristics of matrix diffusion at three dimensions. We
compare the memory function deduced from the field-scale tracer tests well with the computed memory function. Simulation results of the memory function appeared to be coherent with
that measured from the tracer test for a large tortuosity value. Probably, the
diffusion paths are longer, and they are controlled by the properties mentioned
above. From a representative elementary volume of natural reservoirs
studied here, we conclude that, microscale diffusion process in the immobile
domain play a crucial role to better understand the non-Fickian dispersion measured from the tracer test.