Pore radius distribution and fractal dimension derived from spectral induced polarisation
The pore size distribution provides a suitable description of the pore space geometry that can be used to investigate the fractal nature of a pore space or to determine the fractal dimension. The fractal dimension describes the size of the geometric objects as a function of resolution. It can be integrated into the models that are used for permeability prediction. We investigated the fractal dimension of the pore volume of 11 Eocene sandstone samples from China. This study describes an approach to use spectral induced polarisation spectra to estimate the pore size distribution and to determine the fractal dimension of the pore volume. Additionally, the fractal dimension was derived from data of the capillary pressure curves from mercury intrusion and the transversal relaxation time distribution of nuclear magnetic resonance. For samples with an effective pore radius larger than 1 μm, a good agreement exists between the values of the fractal dimension derived from the three different methods, which implies an identification of similar pore structures. Spectral induced polarisation can be a non-invasive laboratory technique for the estimation of the pore size distribution, but the application of the methodology to field measurements remains a challenging problem considering the limited frequency range.