Surface nuclear magnetic relaxation and dynamics of water and oil in macroporous media - art. no. 021605

Proton nuclear spin-relaxation studies on water- or oil-saturated granular packings and limestone rocks allow estimating surface molecular dynamical p arameters. Measurements were performed at various conditions of temperature , magnetic field strengths, and pore size. We show by low field NMR relaxat ion that changing the amount of surface paramagnetic impurities leads to st riking different pore-size dependences of the relaxation times T-1 and T-2 of liquids in pores. These dependences are well supported by surface-limite d or diffusion-limited relaxation models. Surface relaxivity parameters rho (1) and rho (2) are deduced from the pore-size dependence in the surface-l imited regime. We evidence the frequency and temperature dependence of the surface relaxivity rho (1) by field cycling NMR relaxation and relevant the oretical models. The typical frequency dependence found allows an experimen tal separation of the surface and bulk microdynamics in porous media. Sever al surface dynamical parameters, such as diffusion coefficients, activation energies, time of residence, and coefficient of surface affinity, were the refore determined. The methods presented here give a powerful analysis of t he surface microdynamics of confined liquids, which can be applied to the s tudy of oil-bearing rocks.