A General approach to T2 measurements in the presence of internal gradients

Internal gradients, caused by the magnetic susceptibility difference between the solid surface and imbibed fluids in pores, are a frequently encountered limitation in nuclear magnetic resonance (NMR) analysis of porous materials. The strength of these internal gradients are known to scale with magnetic field strength B-0 and their presence prevents quantitative determination of transverse T-2 relaxation times, image intensities, and diffusion coefficients. We present a general method for determining true T-2 relaxation time distributions of liquid saturated porous media in the presence of internal gradients. Our method is demonstrated using water saturated glass bead packs at an intermediate field strength B-0 = 2 T, although the technique is applicable to the wide range of porous media found in nature and industry (rocks, soils, cements, catalysts), thereby allowing these materials to be studied at field strengths previously considered to be inappropriate. (C) 2013 Elsevier Inc. All rights reserved.