Pore-Fracture System Distribution Heterogeneity by Using the T2 Spectral Curve under a Centrifugal State

In this paper, 12 sandstone samples are collected from the Taiyuan Formation in Qinshui Basin, and sample types using the T2 spectral under LF-NMR saturation and centrifugation conditions are classified. Moreover, single and multifractal models were used to calculate fractal parameters of saturated and centrifugal T2 spectra, and the correlation between different fractal parameters, pore structure, T2cutoff value, and pore permeability parameters was studied. The results are as follows. (1) According to the T2 spectrum curves under centrifugation and saturation conditions, all the samples can be divided into three types. There are significant differences in the uniform pore size distribution. However, the non-uniformity of small pore distribution in type B samples is stronger than that of other types, while heterogeneity of large pore distribution is weaker than that of different types. The centrifugal T2 spectrum curve exhibits both single-fold and multifractal characteristics. The results of a single fractal by using a centrifugal T2 spectrum are consistent with those of a saturated T2 spectrum, indicating that single fractal features by using centrifugal and saturated T2 spectra are consistent. Unlike the single fractal parameters, the correlation between the saturation and centrifugal T2 spectrum’s multifractal parameters is weak. This suggests that the physical significance conveyed by the centrifugal T2 spectrum’s multifractal parameters differs from that of the saturated T2 spectrum.