A New Method for Converting T ₂ Spectrum into Pore Radius

Abstract

In this paper, a new method for converting the T ₂ (relaxation time) of NMR (nuclear magnetic resonance) into the pore radius is proposed. Combined with NMR and centrifugation experiments, the relationship between pore radius and T ₂ of the sample was established. The results show that the new method is more reasonable than the traditional method. When the sample was denser and the mercury saturation was lower, the pore distribution curve was obtained by traditional method had a worse agreement with mercury injection experiment, while pore distribution curve of the new method had a better agreement with the mercury injection curve, which reflected the greater advantage of the new method as the reservoir becomes denser. The new method can obtain all the pore information in the sample. The results show that the pores in tight sandstone are mainly consisted with mesopore and macropore, and the connectivity of macropore is better than that of mesopore. The new method can effectively characterize the full pore distribution and the seepage characteristics in different pores interval of tight reservoirs, which had a great significance to evaluate the recoverable resources of tight reservoir.

Keywords

tight reservoir / nuclear magnetic resonance (NMR) / pore radius / T ₂ spectrum

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