A comparison of pore size distributions derived by NMR and X-ray-CT techniques

High resolution micro-X-ray-CT data is used as a “gold standard” to define the morphology of a number of sandstones as well as a carbonate rock. From these micro-CT images the NMR responses to surface relaxation and restricted diffusion in the internal magnetic field are calculated numerically. The NMR response is decomposed into a distribution of relaxation times by an inverse Laplace transformation. By interpreting the relaxation time distributions in terms of relaxation and diffusion modes pore size distributions are derived from the NMR responses. The pore size distributions obtained from an interpretation of the NMR data are compared with corresponding measures derived directly from the X-ray-CT images.