Spatially resolved NMR for rock core analysis

Key words:  T₁ and T₂ NMR method  MRI  positioning analysis  heterogeneity

Abstract:

This research applied low-field MRI technology to rock analysis, and combined MRI and Laplace NMR methods to get more comprehensive information about pore structure, fluid distribution and heterogeneity of core samples. In addition, heterogeneity of cores is analyzed qualitatively and quantitatively. First, the longitudinal relaxation time(T₁) and transverse relaxation time(T₂) distribution of the whole core are compared with that of local regions. The heterogeneity of the core sample can be qualitatively characterized by the T₁ and T₂ difference between the whole and local regions. Then, based on the theory of geostatistics, the experimental data obtained from the multi-layer spin echo imaging experiments are processed, and then the magnitude of the heterogeneity of different core layers is obtained. The results show that the rock core P is most heterogeneous while B is most homogeneous. The heterogeneity of N and P is quite clear in and among layers. In this way, both qualitative and quantitative analyses on heterogeneity of the cores in three dimension are achieved and the correspondence between the two methods is very well. In addition, the SNR is increased by adding multiple pixels in the same local region.