Pore-scale simulation of NMR response

Abstract

The random walk method is used to simulate magnetization decay in porous media. The simulations were performed on images of the pore space obtained using micro-CT scanning and in topologically equivalent networks extracted from these images using a maximal ball algorithm. The simulation results were validated through comparison with experimental measurements of T2 distribution, absolute permeability and resistivity in two sand packs and from comparing predictions on images and networks of Fontainebleau sandstone. In all cases, the comparisons were good, although the networks gave a slightly narrower T2 distribution, implying that some fine detail of the pore structure was lost. This work suggests that imaging, network extraction and pore-scale simulation can be used to predict single-phase transport properties successfully. It serves as a validation for pore-network models and the methods used to generate networks.