PGSE NMR measurement of the non-local dispersion tensor for flow in porous media.

The non-local dispersion tensor provides a fundamental description of velocity correlations and displacement information in a pre-asymptotic dispersive system. Here we describe in detail how PGSE NMR may be used to measure this tensor, outlining the pulse sequences needed for signal superposition, as well as the data analysis procedures. The sequence is inherently two-dimensional, the first dimension giving the displacement resolution, the second giving correlation information. The technique is verified against simulated echo attenuation data from a lattice-Boltzmann simulation.