Nuclear magnetic resonance measurements provide useful insight into pore-scale properties of porous media. One influence affecting the measurement is inhomogeneity in the static background magnetic field ([Formula: see text]). This inhomogeneity can significantly alter the relaxation signal and potentially obscure pore-scale information. To improve the understanding of this effect on the free-induction decay (FID), a measurement still commonly used in practice, a novel methodology is developed to estimate the statistical distribution of [Formula: see text]. A suite of preparatory pulse sequences is developed to encode information about the [Formula: see text] field in the initial amplitude and phase of the FID following each sequence and an inversion is employed to predict the statistical distribution of [Formula: see text]. Knowledge of the [Formula: see text] distribution is then used to correct for the impact of [Formula: see text] inhomogeneity on the FID measurement; this is essential for improving the usefulness of FID measurements for the estimation of pore-scale properties. Results are presented for both numerical and laboratory studies verifying the feasibility of the developed methodology in a controlled laboratory environment, and demonstrating that knowledge of the statistical distribution of [Formula: see text] is sufficient to estimate the impact of [Formula: see text] inhomogeneity on the FID in cases where [Formula: see text] inhomogeneity causes less than an order of magnitude decrease in the relaxation times governing the FID.
Two-photon free-induction decay with electromagnetically induced transparency
