Coal matrix pore analysis using nanoscale scanning electron microscopy and direct capillary pressure curve simulation

This paper presents an analysis of the matrix pore size distribution and simulation of fluid flow in the coal matrix in intermediate-rank coal. The study used scanning electron microscopy images, nuclear magnetic resonance, and mercury injection capillary pressure (MICP) data, which were used to reconstruct the three-dimensional (3D) coal matrix model and analyze the distribution of pores in the coal matrix. The reconstructed 3D model of the coal matrix pore space was further used to simulate capillary-dominated two-phase flow for capillary pressure curves and fluid configuration calculation. The analysis showed that there is good congruence between the simulated and measured MICP curves, which could mean that the described simulation method could potentially be used for modeling the fluid flow in coal. A simulation approach, which was described in the paper, can potentially be implemented to model fluid flow in a dual-pore single-permeability or dual-pore dual-permeability model. Results confirm that the contribution of the coal matrix to the permeability and fluid flow is negligible as a result of the poor connectivity of the pore system in the coal matrix of the studied samples.