A model for the interpretation of nuclear magnetic resonance spin-lattice dispersion measurements on mortar, plaster paste, synthetic clay and oil-bearing shale

Abstract

A model linking the molecular-scale dynamics of fluids confined to nano-pores to nuclear magnetic resonance (NMR) relaxation rates is proposed. The model is used to re-analyse fast field-cycling spin-lattice relaxation rate measurements for the separate water and oil dispersions from an oil-bearing shale [Korb et al., J. Phys. Chem. C, 118, 199 (2014)]. The model assumes that pore fluid can be characterized by three time constants: the surface and bulk diffusion correlation times and a surface desorption time constant. Results are shown to yield meaningful and consistent intra-pore dynamical time constants, insight into diffusion mechanisms and pore morphology. The shale is found to be oil-wetting and the water dispersion is found to be due to the interaction of aqueous Mn2+ ions with bulk water spins. Clay, mortar and plaster paste dispersions measurements have also been successfully re-analysed and a summary of the results is presented. The results demonstrate the wide applicability of the model which advances NMR dispersion experimentation as a powerful tool for measuring nano-porous fluid properties.