A new fractal model for porous media based on low-field nuclear magnetic resonance

Abstract

Fractal geometry has been successfully applied to the study of structures and transport properties of porous media due to its scaleinvariant property. A new fractal probability density (FPD) model is developed to characterize the pore structures of porous media in this paper. Mechanical press filtration (MPF) is performed on pre-dewatered sludge samples in order to achieve different porous structures. The pore structures and water contents of the dewatered porous sludge cakes are then measured by low-field nuclear magnetic resonance (NMR). The pore fractal dimensions are determined with the proposed FPD model based on NMR results. It has been found that the pore fractal dimension increases with porosity under fixed pore size range. The value of the pore fractal dimension of porous samples is larger than 2.6, which indicates highly heterogeneous pore structures. The present work may provide insight on the multiscale structures of porous media based on NMR technique.