An improved method of using NMR T_2 distribution to evaluate pore size distribution

Abstract

Both NMR T 2 distribution of core and capillary pressure can be used to characterize pore throat structures of rock in some degree. Theoretical analysis reveals a correlation between these two sets of data. Determining the transferring coefficient between T 2 and p c is the key step when NMR spectra are utilized to study rock pore throat structure. The available methods using T 2 distribution to evaluate capillary pressure curves result in poor correlation with the real capillary pressure curves. In fact, core space reflected by the existence of membrane bound-water T 2 distribution is different from that reflected by capillary pressure curves. The thesis put out an improved method which uses free-water T 2 distribution to construct capillary pressure curves after eliminating membrane bound-water's contribution to T 2 distribution. Applying this method to some core data we did some analysis and comparison. The result shows an improved precision and indicates that this method can provide reliable principle and methodology support for using T 2 distribution to evaluate pore structure.