Nuclear magnetic resonance determination of surface relaxivity in permeable media

Nuclear magnetic resonance (NMR) experiments are used to characterize microscopic pore structures in permeable media. NMR relaxation distributions are determined from inversion-recovery experiments, and the surface relaxivity is used to scale relaxation to pore size. The surface relaxivity can be estimated from PFGSTE (pulsed field gradient stimulated echo) experiments. The current methods for determining surface relaxivities from NMR experiments are based on asymptotic approximations to time-dependent apparent diffusivity. However, experimental observations within ranges of time for which such approximations are valid might not be possible. We present a new method for determining surface relaxivity from PFGSTE experimental data that is free from such restrictions on experimental times.