Abstract: Both NMR T₂ spectra and mercury intrusion capillary pressure reflect pore structure of a rock, to a certain extent. Comparison and theoretical analyses of NMR T₂ spectra and mercury intrusion pore-throat frequency distribution curve indicate significant correlation between these two sets of data, thus it is possible to calculate pore radius distribution from NMR T₂ spectra. In this paper, several methods (e.g., interpolation arithmetics, methods based on least square principle and other mathematical methods) for converting NMR T₂ spectra into pore radius distribution were evaluated and compared, using mercury intrusion pore-throat distribution data as a reference. Mercury intrusion saturation was considered to be an important factor that can influence the result of conversion. The practical applicability of the methods was tested using sandstone samples. The results suggested that it is necessary to emphasize the main sections of NMR T₂ spectra and mercury intrusion pore-throat distribution, and consider the influence of inadequate mercury intrusion saturation in the conversion process. The conversion result was shown to be more reliable when both the factors were taken into consideration.

Key words: NMR T₂ spectra, pore distribution, conversion coefficient, mercury intrusion, sandstone