Surface relaxivity probed by short-diffusion time NMR and Digital Rock NMR simulation

Abstract

NMR is a powerful technique applied in the study of fluids confined in porous media, offering parameters associated with the morphology and properties of these materials, such as surface relaxivity and relaxation times. It is through the association of these parameters that it is possible to estimate the pore size distribution. However, to estimate the surface relaxivity, the relaxation times must be combined with the pore size distribution obtained by other techniques. As the pore size from the perspective of the NMR phenomenon is not necessarily the same as that observed by other techniques, the estimate becomes strongly influenced by the experimental method chosen. Here it is shown that the surface relaxivity probed by short-diffusion time NMR and the one obtained by Digital Rock NMR Simulation have a good agreement. It is concluded that this behavior can be attributed to both methods working with nuclear spins, which similarly experience the pore space under the same diffusion and surface relaxation effects. • Surface relaxivity probed by first approximation of short-diffusion time. • Comparison of surface relaxivities by two different NMR based methods. • Transverse and longitudinal surface relaxivities for a set of 14 sandstone rocks.