Temperature effect on NMR surface relaxation in rocks for well logging applications

We present nuclear spin-relaxation experiments, at various temperatures and Larmor frequencies for water and oil confined in a series of calibrated porous media and various natural rocks. The temperature and frequency dependencies of the longitudinal nuclear spin relaxation rates 1/T-1, are interpreted with an original model of surface diffusion taking into account the solid-liquid interactions with the pore surface. Depending of the strength of such interactions, one observes an anomalous temperature dependence of the transverse 1/T-2 and longitudinal 1/T-1, nuclear spin-relaxation rates for water in silica and various sandstones and a normal temperature behavior for water-saturated calcium carbonate surfaces. The model supports also the normal temperature dependence observed for oil saturated porous media at proximity of silica, sandstone, and carbonate surfaces. The potential impact of this study for NMR well logging applications is also discussed.